Should you wander down to the Underworld, or get dragged there unceremoniously by Hades, you might find yourself staring into the eyes (all six of them) of Cerberus: the three-headed dog set to guard the Underworld gates. Tales agree that this fearsome beast had three heads, and some even claim he had the claws of a lion and a mane-like ruff of living snakes for extra protection. Scary stuff. Could this be the nastiest pet ever?

Winston Churchill, the cat in Pet Semetary might give Cerberus some competition... coming back from the dead it rips small animals apart without any interest in eating them and starts to give off a strange, decomposing smell...

In 1991 a goat called Snowball kicked its owner in the stomach and killed him. Mind you, the owner had been beating the goat to make it into a vicious guard-goat. (How was that ever going to work?!) Not sure the owner didn't create that problem himself to be fair.

And let's not forget... Cujo!

Dangerous things, pets!