Cujo is the main antagonist in Stephen King's novel and its film adaptation of the same name.
He starts off as being a friendly St. Bernard but chases a rabbit and gets bitten on the nose by a rabid bat. He then kills Gary Pervier and when Joe Camber his owner sees what he has done Cujo attacks and kills him too. Then he holds Donna and Tad Trenton in a car for three days as well as conducting a murderous reign of terror on Castle Rock. He even bites Donna in the stomach and leg but she survives and shoots him down. In the novel, he was killed after getting hit by a baseball bat. However, it is revealed that Cujo survived the gunshot and makes a cameo appearance in Cat's Eye, where he is shown chasing the film's titular cat.