The Descent

You can steer clear of a lot of problems by staying above ground. In fact, there are few reasons to go down there. Few reasons worth dealing with the CHUDS for, anyway. Someone should have told that to these thrill-seeking ladies, looking to do some spelunking after their friend suffers a tragic loss.

The Descent is one of the scariest movies out there, even before the monsters show up. But the monsters aren't entirely pointless... they're effective on their own and they drive the incident. This isn't a perfect movie, but it frequently had moments that flirt with perfection.