Airplane! hands down. Few movies even come close to approaching the funny that is Airplane!. I first saw this in the theater when I was 11 years old. This was probably the first "spoof" movie I had ever seen. At that age I was likely unaware of the genre and just how much fun you could have poking fun in such an outlandish way. I distinctly recall laughing so hard that I fell out of my theater chair and rolled on the cinema floor. I was so weak with laughter that I had a hard time getting back into my seat. And the great thing was that the next, oh, 11 or 12 times I watched it, I would always pick up one more subtle little nugget of comedy thrown in that I had missed on previous viewings.
Also voted for Groundhog Day. Clever and funny and with a heart. Murray at his peak.
Liar Liar was good. Carey's talents really put to good use. Bad Santa was a real hoot.
I gave Singing in the Rain a vote b/c I think it is a very entertaining musical. As a comedy? Well....okay, it had its funny moments.