Jim Carrey's appearance on the show
I found a bunch of episodes of this show on the internet. There is a segment with Jim Carrey (I'm guessing it was during the filming of Dumb and Dumber based on the haircut he had) where he throws a temper tantrum over a botched sandwich order. Oh my freaking Jesus, I havent laughed that hard in a long time.
As far as talk shows guy, I've never seen as many truly Gut busting moments as I have watching the Dennis Miller show.