Good lists up in here.
George Carlin, Bill Hicks, Mitch Hedburg, Brian Regan, Patton Oswalt, Brian Posehn, Maria Bamford, Louis C.K.... I'm sure there are more that I'm not remembering right now.
It's not hard to make me laugh, though...
I have to disagree with Daniel Tosh, though. That show he has, Tosh.0, is one of the worst piles of tripe to ever insult the airwaves.