Lots of cult film debate. I'm just going to put in my thoughts for movies from the last few years that I think might become cult classics with the idea that they are movies that not a lot of people liked but a few people loved. Me being one of them.
Sky Captain and the World of Tomorrow (2004)
My friends and I watch this movie a lot. Its fun to quote from and its got a bit of that "so bad its good" feel you want from a cult movie.
Kiss Kiss Bang Bang (2005)

This is one of those movies that I think just got over looked by the main stream. I show this to so many friends who have never heard of it. Then they immediately love it. And how can you not? Mr Robert Downey Jr. and Mr Val Kilmer. Gold!
Black Sheep (2006)

New Zealand Horror movie about sheep. What else is there to say?
Black Snake Moan (2006)

So bad its so good. Oh and the music is awesome. oh and that tag line "Everything is Hotter Down South".
Superbad (2007)

I think this movie might have actually done quite well, but I think its staying power will prove its cult status.
Napoleon Dynamite (2004)

Someone else mentioned this and I agree. You either love it or you hate it. Perfect conditions for a cult following.
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I've been trying to think of a few more recent movies, but I think that sometimes it takes a little while to find those perfect little movies that fell through the cracks, but I'm looking forward to finding them!