Cantinflas

David Cross
Patton Oswalt
Flight of the Conchords

haha.

Margaret Cho
Bill Hicks (RIP)
George Carlin
Dave Chappell
Chris Rock (He's pretty damn funny)
Bill Cosby (old stand up before the damn Cosby Show)
Wanda Sykes
Paula Poundstone
Ellen Degeneres (Stand-up)
Sam Kinison (RIP)
Sarah Silverman
Ryan Styles
Collin Mockery
Greg Proops

i think dave chappelle is insanely funny

of the people i've seen live i'd say -
jerry seinfeld (funnier than i'd expected)
and in the UK - Johnny Vegas - i saw him right before he became insanely popular in the UK and he made me laugh so hard it hurt, then when people asked what was funny i couldn't really remember any jokes per se - just that he was hilarious

Forgot one:
Eddie Izzard (Stand-up)

Lewis Black
Richard Pryor
Flight of the Concords
Stephen Lynch

Don Juan and Miguel
The Flaming Idiots
Danny Lord
Looney Lucy and Ploppy
Emrys Fleet
Mark Sullivan

The scandalously unmentioned-so-far Eddie Murphy's Delirious and Raw are the best stand up performances ever.

"Now get the me the eggs out of the refrigerator before I smack you in your mouth..."

I mentioned him and am surprised no one else has('cept you obviously).