Birds, bobcats, raccoons, roadrunners, foxes, coyotes and other snakes are all predators of snakes. Young snakes are more vulnerable to predators than fully-grown snakes are.
While some predators see snakes as a source of food, other predators prey on snakes because they see the snake as a threat. For example, cows, horses, antelope and deer are known to trample diamondback snakes because they fear them, but they do not want to eat them.
As for predators that eat snakes, the King Snake is a well-known species of snake that preys on other snakes, and they are known to hunt for snakes specifically, rather than opportunistically.