CoD 4 multiplayer, Countdown map, 6v6 search & destroy game.
I sprinted to one of the far buildings from my spawnpoint and noticed by the time I got there all of my teammates were already dead and they had a UAV and a helicopter up. There was a pile of boxes in each corner with one opening in the middle so I planted one claymore on each corner of the opening, grabbed my trusty MP5 and braced for impact...

The pesky thing was that with my teammates down so quickly and them knowing my location they sprinted towards me and arrived at practically the same time. The first guy came in from the side door, which I was mindful to keep directly in my line of fire, so I took him down relatively easily. Then one came through the front opening and another one from the side door at once. The guy from the main opening was visible to me slightly sooner so I took him down, but the other guy was too far by the time I got him and I had too little ammo in my clip left for a charge around the corner, so I ducked and waited so I could ambush him as he would come round the corner. Apparently I hit him while I was spraying the other guy, because both of my claymores took him out. Knowing I didn't have time to reload, I grabbed the P90 he dropped, which had a full clip and would last longer than the MP5's clip. In the meantime the remaining 3 enemies had come close to the boxes without my knowledge. Luckily, the first one thought I was behind the other pile of boxes and turned round the wrong way, so I immediately decorated his back with lead. I was stupid enough not to aim down the sight, so I wasted half the clip on him (that's 25 bullets). I grabbed his weapon for another full clip and just started shooting, not even looking at what kind of weapon it was because the second dude already had his trigger down on me. I was heavily hit but took him down. The last guy was right in front of me by that time, but my clip was empty. I knew all the weapons lying around had empty or almost empty clips, so I took the only option to sprint for the finish and knife him, which I did! I don't think he ever started shooting at me, because one bullet would probably have killed me.
In the chaos I threw my mouse upwards as I knifed him, presenting all my spectators with a nice view of the ceiling with an overlay of the final score, accentuated with a nice flashing red ring around the edges of the screen. Zekko: 6-0

Everybody went like "wtf hacker" in the chat, and I was on Ventrilo at the time so the guy on vent who was in the server with me was going like "WHAT THE FUCK?!" the whole time xD
I wish I was recording that...

'twas the PC version of CoD 4, btw.

Luckiest as in "survived by divine intervention": Killing a spy attempting to backstab me by rocketjumping in 2fort.

Luckiest as in "the odd of this happening are smaller then the odds of winning the lottery": Messing up a sniper shot in c&c renegade, hitting a stealthed blackhand from the other side of the map instead.

I was playing Starcraft with my friends, and my Korean friend was about to waste us. He disconnected RIGHT before he attacked.

Or in Halo 3, I was playing Shotty Snipers and I missed my target because I can't snipe for crap, but hit the explosive barrels behind him as I fell of the ledge I was standing on.

Shot like 6 guards in a row with a single sniper rifle shot (my last)by headshot in Hitman 2. I killed them all and, though it was just a fluke, i actually shouted "OWNED!" in a room full of people. I went on to die to this computer programmer with a crappy pistol or something of that ilk that level... good while it lasted though.

Halo 3 matchmaking. Playing Multi Flag CTF on Valhalla, I jump on a Mongoose and try to cut off the guy who has stolen our flag. Someone fires a missile pod (homing missile) at me, so I go for a mound of earth next to the blue team base. I fly off it, and jump off my Mongoose in mid-air. The mongoose splattered the flag carrier and his friend, and the homing missile blew up the blue team's warthog with two people in it, bagging me a nice overkill for my trouble.

mine's gotta be on COD4. just got my third kill in a row so i activate UAV, only to find 3 other guys storming the house i'm in. i rush to the door with my mp5 and start firing and take 2 kills. i stop firing and see there's 1 bullet left in the clip, yet when i looked at the radar there's still one guy just outside. he throws a frag through the door and without anytime to reload i sprint in the only direction i could, out through the door. i sprint out, see the guy camping just outside the door, fire, headshot. Best kill ever!

Q3A, regular deathmatch on Q3DM17 (space level, lots of jump pads. If you fall, you die). The Quad damage powerup sits at a platform way above the level. There's also a Railgun in a loner platform way across the map. I was at that platform when i take the launch pad to get back into action (since the Quad powerup had just spawned). Someone on the opposite launch pad decided to go for the Railgun so we were going to collide mid-air. Luckily, i was with the Rocket launcher so i end up rocket-jumping on his face, get propelled way across the map, hit a stray rocket which was meant for a guy on his way to the quad and land on top of the quad, stealing it from the said dude just as he was about to grab it.

On a completely unrelated note, 4xrocket splash damage is a bitch.

Team Fortress 2 - Goldrush, first map, defending. 5 seconds left, a soldier at the cart which is about an inch from the final checkpoint. me, being a sniper rush out, zoom in and quickshot. i got a headshot and won us that round.

Team Fortress 2 - 2Fort, being a scout. they got our intel, rush it back to their intel room, i run after it like crazy and 1 second before he gets it i blast him. then i hear my teammates saying that they are trying to get to me, but at the same time i hear a few enemies coming. they got into the room at the same time so a massive battle ensued as both our and their intel lay there.

Team Fortress 2 - Dustbowl - 3rd level, being a sniper. defending the very last control point was just me, a dispenser, 1 medic and another sniper. the enemy somehow managed to destroy every other person on my team and then they ALL came for us. we killed 2 heavies, 3 medics, a pyro, 2 enemy sniper, 2 soldiers and 2 demomen in 20 seconds without dying.we got accused of being hackers. the other guy left immediately (probably means he WAS cheating), but i just took it as a compliment :)

The one I recall the most vividly, was several years back when me and my brother were playing puzzle bubble 2 on versus mode. We were both with balls up to the line, the scenarios were shaking and the first one to shoot was sure to lose. Fortunately for me his timer was ahead of mine so all I had to do was waiting for his to run out while he just sat back, resigned.

However, when his ball shoots, it hits we-have-no-idea-where and sends half his scenario tumbling down.

We then watch as I got drowned in colourful balls.

(Well, no one said I had to be the lucky one)

Fusing demons in Shine Megami Tensei: Nocturne when the fusion went haywire (1/256 chance of occuring) which results in a random demon. I ended up with level 95 Shiva, the third most powerful in the game, that was awesome.

Half Life 2; Scoring a basket, first time I had the gravity gun, with Dog's ball. That was a total flook.

Halo 3 matchmaking, again. On Sandtrap, someone was charging their Spartan Laser, aiming at the Warthog I'm in. I'm the VIP and fire a pistol shot at him from the passenger seat. Half a second later, my gunner blows up a banshee. Part of the wing goes crashing down and right as the guy fires his laser it hits the wing and the resulting splaser shockwave kills him. Remember that one pistol shot? It hit, and so it counted as my kill.