The Warlock's imp, properly played, is completely broken - it can clear most battles on its own. I don't play Warlock as a first class, but Wyll is always in my party for that reason.
Do tell, seems near useless as summoned but I am always ready to be educated.
I'm not sure I'd agree with using the word "broken" but I do agree the imp is very strong. It's a scout and sneak attack monster with invisibility+hide. Fly gives it amazing maneuverability to zip around the battlefield. In this way it can run interference like a boss.
It hits with it's attack alot more often than you might think it would and often poisons the enemy. And it can be surprisingly hard to hit itself for all but the strongest enemies. The minotaurs might wipe it one round, and maybe one or two other underdark creatures. But mostly, it really has alot of uses.
