Slither (15)

In James Gunn's tongue-in-cheek love letter to schlock-horror, alien-invasion B-movies, a meteorite plunks down in the forest just outside a sleepy mountain town, and a few nights later the square-jawed sheriff ( Serenity's excellent Nathan Fillion) has to deal with high-speed slugs, acid-spitting zombies, and a man who's turning into a ravenous pile of tentacles. It's fun, but it's too knowingly cheap and trashy to have many scares. And, according to one of the immutable laws of cinema, if you don't scream loudly during a horror-comedy, you won't laugh loudly either.