ONE TIME in Black Ops. It was my first time playing Sticks and Stones (only ballistic knives, rocket launchers, an tomahawks). At first, I was sucking, but out of nowhere I just started killing everyone. I started by jumping off a cliff into a small valley and killing two dudes who were fighting, then I just stayed in the same area killing anyone who entered the valley. The whole thing lasted no longer then 30 seconds, but I got at least 10 kills, and I won the game.
It was fucking amazing.
EDIT: Oh yeah, and once I was stuck in a game of Halo 3 with only one other teammate against a team full of some the best players I've ever seen. It was SWAT, with a score limit of 50. Me and this guy(who wasn't very good) actually managed to get the score tied at 49, mostly by being cautious. Then they all teamed up on the other guy, and I got there too late to save him. I got the 50th kill RIGHT AFTER they killed him. Still, it was pretty damn amazing that I lasted that long.