No particular order
Rodney Dangerfield (completely upstaged everyone in Caddy Shack)
Sam Kinison
George Carlin (my all time favorite)
Cheech & Chong ("Dave's not here man")
Bill Hicks
Bill Cosby (I grew up on his albums)
Jim Carrey (I've only seen one of his stand up routines, but it was hysterical)
Robin Williams (best stream-of-consciousness comedian)
Steven Wright
Dennis Leary
Christopher Titus
Joe Rogan
Dave Chappelle (best comedy show on TV ever)
I could go on, but my post would be enormous. I love standup comedy.
How could I forget Dennis Leary... I like his thing about kids being like drunken midgets.
I also loved this Holsten Pils (what ever happened to that beer?) anti drink driving ad in the UK http://www.youtube.com/watch?v=0lTZWUUJrJg I remember them playing it on the big screen in between bands at a festival. 10,000 people around the main stage waving their arms in the air singing A,SS,HO,LE.....