Killer rabbit

Rabbit of Caerbannog

The Killer Rabbit of Caerbannog had a small part in the Monty Python movie: Monty Python and the Holy Grail where it played the part of a vicious protector of a mystical cave where the location of the grail is written on the wall. It (comically) was capable of jumping up as high as a human and biting a human's head off, and it did so with three of King Arthur's knights, when the knights attacked

The Killer Rabbit attacks.

it, despite Tim the Enchanter's warnings. However, Arthur and his knights had to enter the cave, so they finally killled the rabbit with the holy hand grenade of Antioch.

It was also in Spamalot. Some think that the cave's name came from the rabbit itself. It would explain why the cave wouldn't be named the Cave of Aaaugh.