must-see movies

The Honors Program at IUS asked us for a list of "essential" films. It's not clear how you would define the term "essential" with a movie. So I noted that it depends on whether you are seeing films to:

a.) see impressive film-making (in its time);
b.) explore important themes;
c.) experience contemporary cultural relevance; or
d.) catch more obscure films that are impressive.

First, can you think of other categories for recommending movies?

In any case, on that basis, here's the list I came up with (with some effort to categorize by theme/type):

-Crash, Remember the Titans, and Gran Torino;

-Monty Python & the Holy Grail, the Passion of the Christ, Bruce Almighty, and The Ten Commandments;

-Citizen Kane, Seven Samurai, 12 Angry Men, Mr. Smith Goes to Washington, Sound of Music, It's a Wonderful Life, and The Godfather;

-My Fair Lady, A River Runs Through It, Spitfire Grill, Shawshank Redemption, and When a Man Loves a Woman;

-2001: A Space Odyssey, Lord of the Rings, The Matrix, and I Am Legend;

-Eternal Sunshine of the Spotless Mind, Truman Show, Blade Runner, Altered States, Memento, The Green Mile, and Bella;

-One Flew over the Cuckoo’s Nest, Hoosiers, Dead Poets' Society, Schindler’s List, Saving Private Ryan, Unforgiven, Forrest Gump, Braveheart, and Hotel Rwanda;

-Blazing Saddles, Blues Brothers, O Brother Where Art Thou, Airplane, Strictly Ballroom, a classic Woody Allen film, and a Marx Brothers' flick;

-Stand by Me, Parenthood, Fireproof, The Incredibles, Groundhog Day, Princess Bride, and Napoleon Dynamite;

-North by Northwest and Rear Window or Vertigo.

Others to add to the list?