Spoilers etc..

Cod 4:
when Capt. Price chucks you that pistol.
Whilst sniping on multiplayer you spot an enemy sniper aiming right back at you.

Resident Evil 4:
The 'cabin bombardment' level, or the first time you see a guy wielding a chainsaw.

Condemned 2:
The Mannequin cameo *shudder*
The school level torture room.

Bioshock:

When you head down to rapture for the first time
When you see a big daddy for the first time
Most of the medical centre level :D

Seeing the final collosus in Shadow of the Collosus (Because its like 3 stories tall and shoots lazer beams LAZER BEAMS!)

The first time I experienced the "gnome glitch"

Rshady:
Cod 4:
Whilst sniping on multiplayer you spot an enemy sniper aiming right back at you.

Worse - I was on the multiplayer level 'Bloc' on Search And Destory, being chased by four other players. My buddy and I run into one of the buildings through the side door, and sprint down the corridor, alongside the flames and rubble. I notice a few bullets hit the wall in front of us, and we turn the corner. We run upstairs and can hear them following us. We go into the room on the right, and make our stand, holding them off.

As we congratulate each other, I hear the *crack* of a sniper shot, and I see the dust settle inches from my face. I duck and another bullet cracks over my head. Then I heard someone walking up the stairs, inches to my left.

Halo 3 online, just stole the flag with a friend and your driving back on a hog and hear the lock-on beeping on sand trap...when the only thing in a 100 yard radius is sand. "oh.sh-BOOM BOOM BOOM BOOOM BOOOM"...yea thanks, i get it. You blew me up.

Just thought of another, your first sniper head shot on gears where their head goes everywhere!

Jops and Jules dying!!! On the 13th lvl!!!

Old School: Fighting Mother Brain in Super Metroid, then realizing that the boss battle wasn't really over after you destroyed her glass case. THEN finding out, half-way through the fight, that she could kill you damned near instantly with her awesome psychic powers.

Definitly gotta be the chase scene through the apartments in Half-Life 2. After that, I knew the game was going to be awesome.

While on a big boss emblem run on MGS4, you stand up as you crawl into a room, and the guard with super natural eyesight says, "What was that?" and starts walking towards you.

Walking into a room in call of duty 4 while on a kill streak of 25 and hearing the clicks of about 5 claymore mines! The wait between the click and the boom is agonising leaving you just enough time for you to realise you are fucked.

CLICK......SHIT!....... BOOOOM!

In Graw 2 when you lose your helmet.

Oblivion. Going through one of the side dungeons and open a door. five or six enemies in the room, AND I"M OUT OF MAGIKA.

in COD 4 when your sniping whit macmillian and you see all the men coming from the helicopters and from behind the building and they just dont stop coming

In Bioshock, the Big Daddy introduction.

In any game, seeing the Fragmentation grenade coming, and being powerless to stop it. :(

godinshapeofadouchebag:
in COD 4 when your sniping whit macmillian and you see all the men coming from the helicopters and from behind the building and they just dont stop coming

Agreed. That rescue copter was the most beautiful thing I'd ever seen.

I'd rather pick one for a sinle player game, but at the moment the best I can think of is during a game of GTA Race mode on GTA4 a week or two ago, one of my first matches in this mode, on the track around Star Junction.

I'd got out of my car to pick up a gun (I didn't know that you could just drive over them, d'oh) and went back to my car to find that someone was getting into it. I was about to rip him out when alerted to the unmistakeble sound of the horn of an incoming bus.
D:

Resident evil when the zombie dogs crashed through the window
halo 2 when i turned a corner and saw the plasma a second before it hit my face.
and Dead rising when the motorcycle brokedown in the garage in the middle of a zombie swarm.

Mr.Pandah:
Definitly gotta be the chase scene through the apartments in Half-Life 2. After that, I knew the game was going to be awesome.

I thought the same as well, at first. Then all of a sudden, in the middle of that chase, a loading time popped up. Double you tee ef?

maybe when you're playing almost any RTS and you scroll up the map to see a massive army that fills the screen coming your way and you have a army made up of a tank and a few soldiers.

Or when you're playing resident evil 2 and the tyrant smashes through a wall right in front of you

Oh! i've got it! in prince of persia 2, when the dahaka starts chasing you. those bits were real butt clenchers.

When you suddenly realize that maybe it wasn't such a good idea to give a fuel rod gun to a grunt. Especially when that grunt is right behind you in the middle of a firefight...

Dr Steinman. Bioshock.

Pretty much every part of the new Alone in the Dark

voteforyahtzee:
legend of zelda ocarina of time, when you wake up to realize not only are you an adult, but that you kindof slept through the apocalypse.
It hits you when you enter in town square and see that all those happy people were replaced with ya-know, zombie things

Its on page one, but yes, that was epic...

Seeing Kahn from Overlord then realising Im out of all types of minions -_-

everytime i play Rainbow 6 Vegas 2 (Chelsea 0 lol) whenever i turn around and there is somone sneekin up behind me

When you're sniping on the move, and you run yourself into a dead end. Non-camping snipers will know what I mean.

The very end of the good ending for S.T.A.L.K.E.R. I'd used up all my best ammo and weapons just getting there, and then got thrown into a two hour fire fight with no healing meds and only what weapons I stole from the dead. I was so worked up I spent that evening and part of the next day listening to calm, soothing music.

Chrysalids in X-com II. After that I always had scouts in flight armor, and more or less just fragged everything as soon as one Chrissie was spotted.

The first time the Flood ran away from me in HALO II was a good feeling. Also, boxing a silver elite to death on legendary and getting the Hunters to refuse to come into close combat.

That bastard red dragon in Baldur's Gate II casting Heal when I had him down to 1 hp, myself badly in the red and the rest of my party twitching lumps of meat strew around the room. realizing, in BGII, that I'd misplaced an item I needed to advance and I couldn't find it, 100+ hours into the game.

Basically any time when I end up in the middle of a whole lot of hate and somehow come out of it alive.

In Freespace 2 when as soon as you start a mission, theres a six kilometre long juggernaut in your face and your teamate says "DIVE DIVE DIVE" as it hurtles towards your at ridiculous speeds

when i was playing half life 2 episode 1 and was in the museum thing destroying the supression field and i went in a room full of lazers expecting the only thing that would happen is an alarm going off and more combine coming to get killed so i crossed them and turrets started firing. i actually managed to take them down but the button thing didnt work so i was trapped in a room and forced to restart the level by memorizing its code and putting it in the console which i only use when im stuck BTW

Ok, I have to put something in here about Yahtzee's "X Days A Noun" series. I have to say it's a tie between:

OR

Actually, the whole series were packed full of oh.. s**t moments, but I think those were my top two, but it's really hard to decide.

Definately the click from a claymore in hardcore Call of Duty 4

I'd go with the last approx. 3-4 hours of BioShock. not that it's an "oh crap i'm screwed" moment so much as an "oh crap this plot is twisted" way

About every fight in Lost Odyssey.