My friend
People are contributing their lists to this entry. As I write this, it's up to 102 responses and responses-to-the-responses, and I haven't thrown in my two cents yet. (This post is partly a reminder to myself, 'cause of that.)
'Jig outlines the rules at the top.
Onward! Pimp your favorites!
Morning edit: OK, I've added my list. I tried to compile it quickly, and not over-think it, but I think it's a decent cross-section of great films. Of course, I do this an hour from now and that list could be 70% different...