wow. I agree with guttershark but speaking of Donnie Darko...

I can't believe no-one has mentioned Evil Dead. No, not Evil Dead 2 or 3...the first one.

You have to have that one folks.

Others:

The Seven Samurai
Versus
Better Off Dead
Breakfast Club
Real Genius
Watership Down
Slacker (no, not Slackers...Slacker by Richard Linklater).
Spirited Away
Princess Mononoke

I could go on forever.