I wouldn't consider many of the movies listed in this thread as "cult" films. Donnie Darko? I don't know a single person who has not seen that movie. Half like it, the other half (including myself) thought nothing of it after seeing it.
Rules of Attraction and American Psycho, i would agree on. Especially, American Psycho. That movie was a freakshow and I still know alot of people who haven't seen it and those that i've gotten to watch it, enjoyed it.
My Brief List:
Ghost Dog: The Way of the Samurai. Solid movie, not a ton of rotation, but those that have seen it have loved it.
Strangeland - Wanna meet someone you met online? Heh, think again. This movie has freaked out some of my friends.
Unleashed - Once again, not a ton of my people have seen it, but the handful that have put it in their top 3 Jet Li movies ever.