Favorites...
Westerns: The Searchers, Open Range, Unforgiven, Shane, Red River, Stagecoach
Comedies: Bringing Up Baby, Ghostbusters, Monty Python's Holy Grail, Spinal Tap, Duck Soup, The General
Rom. Com: His Girl Friday, Sleepless in Seattle, What's Up Doc, Moonstruck
Science Fiction: Blade Runner, 2001, Star Wars, E.T.
Adventure: Raiders of the Lost Ark, Beau Geste, North by Northwest
Film Noir: The Maltese Falcon, Touch of Evil, Strangers on a Train, Night of the Hunter, Out of the Past, Notorious
Epic: Lawrence of Arabia, Ben Hur, Spartacus, Reds
War: Patton, Sgt. York, Apocalypse Now, Bridge on the River Kwai, Shindler's List, The Longest Day, Henry V, Casablanca
Legal: To Kill a Mockingbird, 12 Angry Men, A Few Good Men, The Verdict
Fantasy: Wizard of Oz, Lord of the Rings, Field of Dreams, Groundhog Day
Christmas: It's a Wonderful Life, Miracle on 34th Street
Ye olde period pieces: A Man for All Seasons, The Lion in Winter
Catch all: Singing in the Rain, The King and I, The Godfather, Mr. Smith Goes to Washington, Duck Soup, Shawshank, Pulp Fiction, The Sixth Sense, We're No Angels
A sampling at any rate. Leaving out a lot of modern stuff and, I'm sure, a number of my favorites that aren't occurring to me at present.