Non-clique: Gordon for sure, though I'd say Sheldon and Ray have a major dick side to them. For example, Sheldon says "I can't wait until I'm big enough to do this to someone" when swirlied, and Ray's VICTING (bullying) quotes indicate he actually seems to want to bully people (especially his quote "Get used to this, 'cause THIS is going to happen every time I see you" xD).
Nerds: Hmm...I'd say Algie as well. But a lot of them are dirty pricks in their own ways.
Bullies: Hard choice between Trent and Davis.
Preps: Aside from Derby, easily Tad, though Justin is a close second.
Greasers: Hard choice...Peanut has his bad moments, but the hard part is choosing between Lucky, Hal, Norton, and Lefty.
Jocks: Probably Damon.
Townies: Hmm...difficult choice between Omar, Otto, and Gurney.
Girls: Difficult choice between Eunice and Mandy. I'll go with Mandy though, because I take most pleasure in beating her up out all the girls. xD