No doubt in my twisted mind that WC Fields tops the field.
He could make you laugh just by picking up a pool cue.
Other favorite comedians/comediennes are Steve Allen (especially his skits with Charlie Weaver!), Phyllis Diller, Eve Arden (of Our Miss Brooks, Red Skelton, Jackie Gleason and Jonathon Winters.
Special honors go to Lenny Bruce. Lost in all the controversy about his revolutionary subject matter is the fact that he was, and still is, downright funny. And Mort Sahl, whose political lampoons kept him mostly out of the public eye.
Finally, I have to mention Oscar Levant, concert pianist and companion of George Gershwin. He ad libbed more great one-liners than anyone except Yogi Berra:
"There is a fine line between genius and insanity. I have erased this line."
"I was kicked out of the mental hospital for disturbing the other patients."
"I'm going to memorize you face and throw my head away!"
"I am no more humble than my talents require."
"Happiness isn't something you experience; it's something you remember."
"Underneath this flabby exterior is an enormous lack of character."
"The only difference between the Democrats and the Republicans is that the Democrats allow the poor to be corrupt, too."
Yogi Berra, on low attendance at baseball games: "Well, if the people don't want to come out to the ballpark, how you gonna stop them?"