A List of Underappreciated Movies

From the good tech folks over at Slashdot: What's your favorite underappreciated movie?

Lots of interesting answers, and I'm taking a few as recommendations.  Even though I didn't post over there, what to add?  I see that Primer made the list; from the same guy there's Upstream Color.  Not to be missed!

After that, if you just want a good popcorn-muncher B-movie, it's hard to beat Reign of Fire.  "Only one thing worse than a dragon."  (watch the youtube clip at the link to find out what that might be)