I go by "Knifey Spoony" in Counter Strike: Source.
If I'm taking someone on:
"You call that a knife? This is a knife!"
If someone pulls a knife on me:
"That's not a knife, that's a spoon!"
If I die:
"Alright, alright, you win. I see you've played knifey-spoony before."
Cookie to anyone who gets it.
In Half Life 2: Deathmatch, I often quote Star Wars.
Kill:
"VENGEANCE!" (Probably from SW considering its penchant for hammy acting and dialogue, but possibly not.)
After a marvellous run:
"Do, or do not. There is no try."
Losing/dead/playing against someone very good:
"The Force is strong with this one."
Yes, I live in hope that one day, when I say "If you'll excuse me Master", and leap off a building/flying vehicle to land safely below, someone else will say "I hate it when he does that!"