Squirm
The success of Willard, in which a young man trained his pet rats to kill at his command, inspired a rash of horror films featuring animals run amok, including snakes (Stanley), frogs (Frogs) and even rabbits (Night Of The Lepus).
Squirm was one of the more interesting films spun off this subgenre, in which a town is terrorized by bloodthirsty worms who've been angered by a downed power line during a rainstorm. Better than it sounds, and packs a few good scares (especially if worms make you squeamish).