How about Raising Arizona?

Another fantastically funny actor that never got credit was Gregory Hines.

Great dancer and hilarious onscreen.

I saw another funny movie last week - 'Happy, Texas' with Steve Zahn and William H. Macy

Anchorman and Old School. A couple of my favorites. I also liked Step Brothers.

Rolemodels and The Hangover are deffinately worth a watch!

A couple of oldies need mentioning:

It's a Mad Mad Mad Mad World - possibly the funniest movie of all time.

Hatari with John Wayne doing a comedy.