Primer is an indie Canadian film that won the Grand Jury Prize for Drama for 2004, in case you care about such things.
Me, I care about smart films with great premises, and in this, Primer delivers in spades. Sure, there's plenty of pseudo-physics hand-waving to make the premise work, but hey, some of the best SF films are the ones that are about the story, not just the tech (nothing wrong with good tech, I'm just saying).
Primer begins slow, with what any veteran of a Start Up will recognize as way too much product development verbiage, but this thins out a bit thereafter, leaving us with two interesting characters and, well, a neat box. I can't really describe it in much more detail without giving things away.
Primer has a very indie Candadian feel to it, and those of you who have watched
Cube will spot weird little similarities in set, lighting, and accents. Primer, however, has very little real violence and will not gross you out in any way. It may, however, leave you puzzled as hell. But again, I can't go into that without giving things away.
Anyway, Primer. Available on DVD. Joe Bob says check it out.