Thought of another one.

The Rage-Quitter
Complete jackasses, these players will quit at any point in the game if they feel like either A) They're losing, or B) Their team will lose. They do not have the common decency to complete a game, and apparently dislike the experience of losing. Egocentric to the max, they feel that they are too good to lose, and if they're not in the winning position, it's someone else's fault. Unfortunately, there is no way to get rid of them, but they're still fair game to rant about during lull periods in the match.

I find these guys to be uncannily common in Left 4 Dead.