I have a lot of characters, maybe close to like about 200ish or something, with some generous rounding off. But the one character I always really want to play, and rarely get to, is the assassin. Like a /true/ assassin, aligned with evil or neutral/evil, master of the shadows and the dagger, nameless, faceless, cold, ominous, fear-inducing blackmailer.
Of course that almost never works well in a roleplay simply because roleplays rely so much on character development and requires social participation, the two things that seriously conflict with that kind of character to the point where it's nearly impossible to pull it off XD