Well, if you want something that makes you think, don't get any cheap comedies or movies about weed. They just get you sitting there laughin' your stoned ass off. Here's a couple I enjoy:
> Eternal Sunshine of a Spotless Mind (relativley serious even though it features Jim Carey, and it's trippy as all fuck)
> Trainspotting (should get you thinkin')
> Clockwork Orange (classic Kubrick)
> Constantine (that's if you're in a 'think about religion' kind of mindset)
> Passion of the Christ (makes you consider what Jesus evidently went through, even if you're not a religious person)
> Donnie Darko (just plain awesome)

Fuck. I can't think of any more. Oh well, try them.

Peace