Since Mr.Falcon already picked the low hanging fruit(s) I'm forced to dig a little deeper.
First, it bears mentioning again...Jay Leno is NOT funny. He spews out middling drivel for Walmart nation.
Not funny, overrated: Howie Mandell, Yakof Smirnoff, Jeff Foxworthy, Louie Anderson, Sandra Bernhard, Sinbad, my uncle Gifford
Funny: George Carlin, Bill Hicks, Mitch Hedberg, Louis CK, Ricky Gervais