When it comes to humanoids my favorite has got to be the goblin. Goblins are the forgotten roadkill you pass over on your way to the dungeon - or at least that's how they are in most of the campaign's I've played in. But as any player in my campaign can tell you a goblin is the thing you'll fear the most even during high level play.
With a 10th level goblin I have killed twentieth level characters. I have killed 15th level characters with base goblins (seven to be precise), without giving them addition hit points, or undue advantage.
Goblins are the shit.