I'm way over 10, but they're in 2 categories, at least. By the way, I'm sure I'm missing quite a few, but this is most of them... and like the very first post said, these aren't what I consider the best, they're just my favorites. You know, the ones I can watch over and over again. Oh, and they're alphabetical order, not preference.
More Serious:-12 Angry Men
-Amarcord
-A Streetcar Named Desire
-Casablanca
-Cat on a Hot Tin Roof
-Cinema Paradiso
-Cool Hand Luke
-Il Postino
-Rope
-Rounders
-Strangers on a Train
-Tango (1998)
-The Godfather 1&2
-The Hustler
-The Magnificent Seven
-The Man With the Golden Arm
-The Outsiders
-The Professional
-Who's Afraid of Virginia Woolf?
Not-So-Serious:-A Mighty Wind
-Bells are Ringing
-Born Yesterday
-Carefree
-Charade
-Clueless
-Dazed and Confused
-Gentlemen Prefer Blondes
-Harvey
-Houseboat
-Lover Come Back
-My Favorite Wife
-Nueve Reinas
-Ocean's Eleven (Both versions)
-Sabrina (The original w/ Bogart)
-Shall We Dance (Fred Astaire, not J.Lo!)
-Sixteen Candles
-Singin' in the Rain
-Snatch
-That Touch of Mink
-The Odd Couple
-The Philadelphia Story