Wow, I realised I haven't told what is perhaps my best gaming moment.
In school, some guys (younger than me) were playing Aliens vs Predator on the network. I noticed it, silently joined their game..... and slaughtered them all.
Their reaction: "Who's Angrist!?!?"
Classic.
BTW I was a predator while all the others were marines. Since the game is so dark, they never saw me coming. I didn't think they killed me once...
Having a score in Perfect Dark deathmatch that's twice as high as everyone else is quite satisfying as well.