TNG: Data, Picard. Everyone but Worf.
DS9: Dukat, Garak, Weyoun. I like all the characters except Kai Winn. Dukat is my favorite ST character ever, though.
VOY/ENT: none, because I haven't seen the entire series of either. I plan on going back and watching them all, but I get distracted sometimes and re-watch the other ones instead.