2001,
Moon, and
Children of Men are all great, though if you've never seen
2001 before be warned it's a little slow.
Sunshine is a fantastic artsy film, but the science is abominable.

If Anime counts, then perhaps try
Akira or
Ghost in the Shell.
Primer, for an excellent depiction of the discovery of time travel and its implications. It also has the most confusing plotline of any movie ever made.
District 9 is a very interesting take on a post first-contact scenario; highly recommended.
Red Planet, maybe? Mankind has attempted to terraform Mars, and something went wrong. A team is sent to investigate.
There's always
Serenity.

That's all I can think of at the moment.