There is a particular group of movies that hold a special place in my heart. These are the movies to which I make my references, of which I am continually reminded, and about which I chuckle to myself.
The Awful Truth
Bringing Up Baby
The Philadephia Story
Monty Python and the Holy Grail
A Fish Called Wanda
Dirty Rotten Scoundrels
The Big Lebowski
The Forty-Year-Old Virgin
I wish there were a Shakespeare movie to put on this list, and Brannagh's Henry V and Much Ado About Nothing come close, but they don't quite make it. Also, except for Casablanca, this is obviously a list of comedies. Movies such as The Third Man would be on the list if it were broader. Casablanca is on it because it's friggin' Casablanca.
N.B. People whose taste I trust completely hate some of these movies (especially The Big Lebowski). That makes them no less awesome in my humble opinion.
P.S. If you're a Buster Keaton fan, my apologies. I've never enjoyed anything I've seen by him, and, like a good film student, I've tried. I thought his cameo in Sunset Boulevard was funny.