I picked up Napoleon Dynamite at Hollywood Video, previously viewed. Came in the original case w/insert, great condition. It was $14.99, and the store ran a B1G1 Free promo, so it only cost me $7.50 in reality.
I didn't fully understand Donnie Darko, but thats because it was a cerebral type movie... I couldn't understand ND because I think I have a fully functioning brain...
I guess you either love it or you hate it. There isn't a point to the movie, but I found the characters hilarious. Don't expect a plot or anything in-depth, but I think it's definitely worth seeing...it has an off-beat humor that's not quite slapstick, but not conventional either.