[Protoclown]

George Carlin
Bill Hicks
Lewis Black

Though the single funniest stand up comedy cd I have heard is Dave Attell's "Skanks for the Memories".

I prefer comedy that has some social relevance though...and while Attell can make me laugh more often and harder than the top three up there, it's more of a pure entertainment value rather than actually making some good observations about society that get me thinking, while making me laugh my ass off.

Honorable mention:

David Cross
Eddie Izzard