Bill Bailey is hilarious. Zappa's humorous works are also very funny esp. "Bobby Brown Goes Down", "Dinah Mo Hum" and all of "Joe's Garage" think for me though the funniest is a Wild Willy Barret track where he saws through his guitar while playing it. (Sorry can't remember the name of the track, i'll edit this when i go round my mates and get him to put it on)

Also "Headbutts" by John Otway is damn funny too. Heres a version with Wild Willy Barret on it too YouTube - Wild Willy Barrett and John Otway