A classic for me (and others... apparently it turned into a case study in emergent AI behaviours during test) happened in Halo 1; when going through the Forerunner rooms in Assault on the Control Room I ran into a sword Elite and backed up so that there was a glazed window between me and him... the Elite then smashed the window with his sword and climbed through. Reflex alone let me plant a sticky 'nade on him as he clambered over the frame... my conscious mind was too busy gibbering.

-- Steve

I think one of the gaming moments that stands out the most for me was in F.E.A.R. Extraction Point's Demo, which I had checked out before buying the first game. I distinctively recall a point where you go down a hallway to a doubledoor which leads to a massive room with lots of spiffy short walls and pillars (people who played the game might recognize it as the place where a huge armored thing busts through the wall and tries to mow you down). The reason I remember it is I got caught in a huge gunfight and was pouring fire on a guy behind a pillar when he ran out to the side and did this awesome looking slide behind one of the low walls, returning fire as he slid, and without missing a beat immediately blind-fired on me from his new (if low) piece of cover. I thought it had to be scripted, but when I redid the fight, it never happened again, leading me to believe that no scripting was involved.

I was playing Company of Heroes the other day, and I remember killing a troop with a Recoiless Rifle. The poor guy goes flying from the explosion upside down directly into a nearby tree, which he bounces off and flops to the ground. This kind of physics in an RTS? Awesome sauce.

twilight princess- beating ganon with a fishing rod.

GTA IV- I stole a cop car with some twat they'd arrested in it and when I escaped the wanted area he promptly got out and tried to take the car back.

I stole a different cop car with a cop still in it, then escaped the wanted area, when he got out he thought absolutely nothing was wrong and went on his merry business.

AndyMacK:
Can't remember the game - probly Asasins Creed - I shot one of a pair of guards, the other walked on for a moment, stopped, turned, looked at the body for about 15 seconds, turns back, says "It must've been the wind" and walks off.

That happens frequently in Splinter Cell, and it's hilarious every time. I like to imagine it from the guard's point of view:
It's another quiet night here at the CIA headquarters in Langley. Oh, there's my partner, Eric. Hello, Eric. He patrols the west corridor, I patrol the east.
Hmm.
In the dim light of the east corridor, I have just seen a man in black grab Eric from behind, knock him out, and drag him into the shadows. I'd better go and investigate.
...
Well, I can't see anything except those three green lights at eye-height at the end of the corridor. It must have been the wind.

True Crime: NYC had a couple of weird things happen because of AI, but the only one I can remember off the top of my head is that when you're driving down the street at full-speed pedestrians will dive to get out of the way of your car.
Except... more often than not they dive into the path of my car, from which they would have been completely safe if they had not leapt in the first place.

There's a few good AI routines in Legend Of Zelda: Wind Waker, though because they're scripted they don't really count. But they bear mentioning anyway, I think:
When a Moblin swings for you with his spear and hits another Moblin, he will look at him with a bizarre expression on is face, which I assume is surprise.
And the skeletons have the best one: break one apart and then steal its club. It'll start to advance on you when it reforms, realise it doesn't have a club, tear off its own arm and use that instead.

Oblivion (Oh god not another one) ...Basically, the count of Cheydinal had the NERVE to put some tantalising emeralds in the display cases near him. I sauntered over and swiped them due to my terminal case of magpie syndrome, and obviously i got nabbed. So, i paid up, and went to go back into the castle to go to the prison so i could get my stolen stuff back.
Or, i WOULD HAVE if i didnt get re-arrested for something involving 5 bounty. I paid up again and reappeared outside the castle (again) ...and Count Cheydinal was outside.
...and the gaurds suddenly piled him, knocked him unconcious and walked off.
...Someone PLEASE explain that to me.

The frog battle in act I: if you go behind the 2nd set of frogs that jump from above below and you run across from meryl et al., they jump down, look at you, then turn around...and shoot at meryl, forgetting about you!

Good stuff.

Some of the Halo 2 and 3 AI's are good. Surprisingly, they can actually do fairly well against snipers, such as the Outskirts and the "Jackal Cliff River" on the first Delta mission(on that same mission however, a sniper marine blew himself up with a plasma array--while he was shooting a jackal corpse). In Halo 3, anytime you need to sneak up on an encampment behind a wall, the marines or ODSTs will quickly and quietly slaughter the snoozing grunts, or at least get into a good covering position, and then actually wait for you to lead the attack. They don't blunder into the enemy and blow your cover or their own. Plus, leading a platoon of weapon-customized factory workers and marines in a final charge up AA hill looks, feels, and sounds awesome, especially if one of them has a fuel rod gun.

I was playing Metal Gear Solid 4 on my friends PS3 the other day (too cheap to buy my own). Having never played a metal gear solid game before I started out on Liquid Easy and played the fist level.

While sneaking around I get to the point where I have to duck under some rubble and crawl under it to the next building. All of a sudden I see one of the friendlies get thrown down right in front of me. He looks up at me, stretches one hand out in supplication and says "Please Help me!!" before the PMC guns him down right in front of me. He then makes a few gurgling noises and crumbles to the ground.

I though for sure it was scripted. But no matter how many times we replayed the mission it never happened again. It was probably the single most amazing moment of AI I've ever seen.

On a lighter note, in Elder Scrolls Morriwind I played a stealth character with two enchanted rings and one enchanted amulet. All of them with Chameleon constant effect. (Which was much harder to do than it is in Oblivion. Fucking Golden Saints) Anyway, the combined chameleon was over 100% so I was completely unnoticable to every character. This was funny when I reached the point that Ash zombies spawn whenever you try to sleep. I went to sleep in my big fancy house and I am awakened by a Zombie over my bed. Of course he can't see me. All he does is walk around shouting "Master!! Why can't I hear you!!!" I decided not to kill him and named him Fred. (Some quirk of the spawning meant that even when I took off my enchanted items he didn't treat me as an enemy.)

The original F.E.A.R. had some of the best AI ever, no joke.

This one time, I was exchanging fire with a group of Clone Soldiers down a long corridor, ducking behind my little pillar whenever they returned fired. Now, this went on for a little while, until they suddenly changed tactics, and caught me off-guard.

There were three of them. One tossed a grenade at me, forcing me to stay under cover, while the other two rushed me. The closest one kept me pinned with rapid fire, while his mates ran for my pillar. I managed to kill one, but by this stage, the other two had taken cover on the opposite side of my pillar.

Now, this is where they fucked me royally. Such a simple trick, and I fell for it.

One of them, the leader I assumed, called out "GO LEFT!". Naturally, I check my left flank, and sure as taxes, one of them is trying to sneak up on me. I waste him easily. Revelling in my easy victory, I forgot the last bloke... Who came from my RIGHT flank.

The bastard had a shotgun, and blew me into a fine red mist of gore.

Oh got one! This isn't a very popular game, but on James Bond 007: Everything or Nothing on a motorcycle level when your driving against traffic, civilians driving two lanes away from you will swerve in to you.

I never found the F.E.A.R. AI to be terribly fantastic. Though there was this one mission where you have to escort that stupid blonde bitch out of the Armacham building. We were going in the elevator and the script was for her to say "Why are all the lights going on? Get ready!" and for the elevator to stop. The not script was the soldier who threw a grenade a split second before the door opened, so I had no chance to move out of the way before it exploded and killed us both. And I don't even think she died. God knows how many times I shot her in the head hoping she would die.

The Potato Lord:
Oblivion, I was going into an oblivion gate to save the duke of Cheydinhal's son,and when I finally meet up with him. I'm told I have to help close the Oblivion gate while protecting him and his one surviving buddy.Ok fair enough, but at the first Freakin' deadra we see they both charge it which causes it to turn towards the lava, fall in, and die. BUT, thats not the best part. the Son in all of his brilliance decides to jump in after the deadra and get himself killed. Even after that feat of intelligence, The son's buddy decides to pursue the deadra as well and jumps in too.Thus, my reward is effectively ruined by suicidal escortees.

Radiant AI, isn't it?

Hey, this happened to me too! Except the friend didn't follow.
My personal moment had to be when I pick pocketed Lex's Claymore, and he still fought me. I beat him senseless with his own sword so many times.

I've had a number of good moments; but none spring to mind...
except one that happened about 2 weeks ago.

'Kay, so I'm playing fallout 2, I'm in a battle with some gangsters, and I have the cyber-dog and Myron with me, . I have 2 of the gangsters in my sights, and I switch out my guns to get out my mini-gun. I wait for my next turn, but Myron AND my dog also run into my field of view.

SCREW THEM ALL.
The cyber-dog was the only survivor.
BWAHAHAHAH.

Oh, here's a popular one from Fallout.

Ian... SMG... you all remember. It's the reason I only give him pistols to use.

EDIT: Oops.

Enemy general rushing past all his troops to charge my troops (to the very centre of my battle line, naturally), dying and then sending his own troops to chaos in Rome: Total War.

In Medieval 2: Total War, I was playing a custom battle as the Scots, with a line of pikemen units at the front, flanked by highland nobles, with some peasant and highland archers behind them. At the very back of this formation, I have my general and his mounted bodyguards, as well as 2 or 3 units of pike milita who are acting as reserves. The battle wears on with the enemy forces being decimated by row after row of pointy tipped death, and eventually they begin to flee en masse. As pikemen are horribly slow, even when out of the spear wall, I sent my archers chasing after the surviviors, and set my general and his entourage off to run down the stragglers. However, as my general's unit moves through the pikemen standing in front of them, the pikemen start stabbing the horses, killing my leader and all but 6 of his guards.

I promptly re-watched the battle replay, and instead of being stabbed, my general rides amongst the pikemen unharmed, which confused me further.

This is still the only time I have lost units after winning a battle.

Has to be in the original Socom for the Ps2. I'm overlooking a terrorist encampment on a cliffside. My AI squadmate BOOMER walks over to me, crouches down, zooms through my head and fires trying to take out one terrorist.

Let's just say he missed and I had to restart a mission.

Camarilla:
In Medieval 2: Total War, I was playing a custom battle as the Scots, with a line of pikemen units at the front, flanked by highland nobles, with some peasant and highland archers behind them. At the very back of this formation, I have my general and his mounted bodyguards, as well as 2 or 3 units of pike milita who are acting as reserves. The battle wears on with the enemy forces being decimated by row after row of pointy tipped death, and eventually they begin to flee en masse. As pikemen are horribly slow, even when out of the spear wall, I sent my archers chasing after the surviviors, and set my general and his entourage off to run down the stragglers. However, as my general's unit moves through the pikemen standing in front of them, the pikemen start stabbing the horses, killing my leader and all but 6 of his guards.

I promptly re-watched the battle replay, and instead of being stabbed, my general rides amongst the pikemen unharmed, which confused me further.

This is still the only time I have lost units after winning a battle.

Pikes hurt cavalry even when they are not attacking. Replays are notoriously buggy since they only store the commands you and the ai gave and not the game play itself so more often then not catapult shots are all messed up. In some cases, especially around artillery, the battle may even have a different outcome. Think units trying to charge a breach.

Back on topic: CoD4's grenade saturation bombing feels like an artificial way to make the game harder instead of actual ai.

The Ptolemaic A.I. opponents in RTW can be incredibly annoying. They'll just sit there, in the middle of a bloody sandstorm, watching you. The times they'll move first is if they outnumber you, or have plenty of chariots.

yet another oblivion one. i'm not sure if this counts and everybody has probably seen it aswell, but whatever. I'm talking to lady in an alchemy shop and in casual conversation she asks me what the fine for necrophilia is in cyrodill. i thought it was funny.

Morrowwind: those damned guards have eyes in the back of their heads, or have divine hearing!
Ridiculous!
Anything on Legendary in Halo 3 is murderous. If those brutes see so much as a centimeter of your green hide, they will grenade you to oblivion. Also, sometimes grunts will do grenade volleys.

Yet another Oblivion moment of hilarity:

My sneaky Marksman-preferring thief Khajiit stumbled onto a bandit encampment along the shores of Lake Rumare one morning, getting the attention of one of the bandits before I could get into stealth. As I draw my bow and nock an arrow, the claymore-toting Redguard bandit rushes at me- and then makes a sharp left turn at about ten feet away, rushes down to the lakeside and slaughters the hell out of a mudcrab.

By the time he'd turned back to me I'd just let a Dwemer arrow fly at his skull.

Someone on Assassin's Creed somehow grabbed me near a Memory Block Wall, then tried to throw me...But then clipped through the memory block. ...i just stood there as he continuously ran at me like he was on a treadmill, but he couldnt get back through...
...Eventually, i went over and tried to assassinate him with the blade, it worked...And i went through the wall.
Unfortunately, the game crashed after that.

When you say "Bad AI", I immediately think of S.T.A.L.K.E.R. !

---Funny moments in the game---

First Nostalgic moment-
I was on the way to the Agroprom Facility to help the fellow Stalkers fight off the military, as the fight was almost nearing its end and I was in the middle of the facility with a couple of fellow stalkers mopping up some soldiers. Out of the blue comes a pack of dogs, a Flesh (mutated pig running around in circles being chased by the dogs then two Bloodsuckers came out of the warehouses (I guess because it was dusk). It was literally chaos NPCs were running amock the soldiers were changing their targets every second lol, one shot being fired at a dog then at the bloodsucker trying to hump their face off.

The Stalkers were shooting the dogs ---that were chasing the fleshs - which were being attacked by the bloodsuckers - that killed the soldiers lol!

Nostalgic Moment 2-

"The Whirlygig of doom"

Near the Yellow teams base (cant remember their names) there is an encampment with three Stalkers, as I was talking to one I heard lightning bolt flashes from the corner and saw that a Bloodsucker was coming over the hill towards us. I was still in dialogue with the NPC but they all ran off in the same line past the caravan towards a whirlygig and and got super compressed into a meat chunk lol , but to top it off because I was still in dialogue I was still having a conversation with the person but then when I accepted the mission it automatically failed because he was dead lol!

This is just the most memorable ones, to pick a couple from thin air would be the Teabaggin NPCs next to the campfire and TK'ing AI.

rowan-thats-me:
im off to plat oblivion now, if anything crops up, which im sure it will, ill tell you, oh and heres one anyway, i was sneaking throught the temple of moths and i got a little close to one of the blind monks, who said "I'd better keep off the ale, im starting too see things!"

This made me laugh so hard!

My own experience is how human adversaries will always cry "Enemy is everywhere!" over and over in Mass Effect, despite the fact there are only three of you hiding in a single doorway.

That's another reason to avoid the side quests.

I swear this happened I am not lying, I was playing Halo 2 on first part of the second lvl. and a grunt yells out, "That's it, I quit! You guys suck!" and throws down his weapons.

I also love how the beggers voices in oblivion switch between lines.

I think that Deus Ex is the king of this thread.
1) They gave you the capacity to pick up and move dead bodies, but didn't give the enemy the capacity to respond *at all* if they encountered a corpse lying on the floor.
2) The flamethrower counted a "silenced" weapon as it made no noise- and neither did enemies who were aflame. Even if they ran past other guards, as they thrashed around on fire, their comrades took no notice. Maybe I just happened to shoot the unpopular ones, I don't know.
3) Has anyone seen that video of getting all of UNATCO fighting a vaccume cleaner?
I can't find it myself, but the AI is priceless in other places.
http://www.youtube.com/watch?v=T4-TUwxFKgQ
for example.

Another new one from me. Halo 3...One of the little enemy midgets...I think he finally ROFL'd himself completely insane. He threw a sticky straight up into the air, then walked forwards about 2 millimeters....and it came right back down on his head.
This alone was brilliant, but when he yelled "NOT AGAIN!" I nearly passed out with laughter.

Once in Morrowind I walked through a small village and suddenly felt like killing someone. Ok, enter the nearest building. (It was the slavequarters.)Inside is some girl or really small woman. "Easy" I think but after my first blow lands she picks up a katana (larger than herself) from nowhere and kills me with 2 hits.

In Oblivion (again) in the mountains just outside Bruma, I sat and watched two Imperial Legion foresters firing arrows at each other for about 5 minutes until finally one of them died. So i went over and looted his corpse.
Also on one of the Mages Guild missions you have to investigate a rogue wizard robbing and killing people on the highway. I set out followed by the two battle mages who are sent to help you. I killed the rogue wizard, the male battle mage summons a zombie, a passing Legion soldier runs over and attacks the zombie, then proceeds to murder my battlemage companions. Classy!

Blood , for PC. I was playing co-op with a friend, we are killing psycho people with tommyguns in the circus area... so my friend goes in some kind of small tower to kill a guy thats shooting us by the window... in the meantime I trow a grenade in the window not thinking my friend is in there... I see my friend jump out the window right as grenade explodes and send the mod flying right behind him out the window and on the ground. ehehe nice sight.

In Halo 1, there are some levels where you fight the covenant on these bridge thingies, which have lots of wall sections sticking out that are just perfect for taking cover behind. anyways, the AI is smart enough to realise this and will take cover beind the wall sections... however what they don't realise is that they are right up against the edge of the bridge... and as such hilarity ensued when instead of jumping to the middle of the bridge to avoid grenade, they would rather evade grenades by jumping over the side of the bridge. just FYI this worked with the Hunters too(giant blue armor plated guys).

In Twilight Princess, I've noticed that if there's a bunch of "vanilla" enemies (bokoblins, lizafols, bulbins), and you shoot one, everyone will run over and check out the corpse.

This works especially well with bomb arrows..

One that might be more of a glitch than AI, but in Hitman2:SA, there is a level in Japan, in the middle of a blinding blizzard with lots of guys in ninja suits on guard. Every time you steal a ninja suit and get spotted by an enemy (300 miles away, thru aformentioned blizzard whiled garbed head-to-toe in an all concealing ninja suit) the cocksucker immediately raises the alarm!