The Mist -- aka Move On, The Movie.
Plot summary: The US Army opens a transdimensional portal to the overpopulated home of Cthulhu. All hell breaks loose, trapping a bunch of good citizens in a grocery store. Severely scary things happen, civilized behavior ends, and good people have to deal with it.
The biggest scares in this film come from the people in it, not the beasts unleashed, making it more drama than horror. Granted, it still has plenty that makes it a horror film, despite the liberal agenda introspection that occurs. However, that examination of where liberals stand goes through many gyrations in the film: the stand-in for the "religious wrong" is actually a heretic, and core religious (or common-sense if you're not into the labelling party that is modern politics) messages come back in a big way at the end of the film; the military may have opened hell up, but in the end, our Army cleans its carp up and saves the day.
It's disconcerting to think that a horror film has a better discussion of contemporary issues than our news media. I guess that makes it a horror film on multiple levels....