I'm not sure I'd want to be big and hairy, but regrowing a lost limb would be great! Scientists trying to genetically engineer tumours in mice have accidentally created a mouse version of Wolverine (but without the big claws).
The mice produced a protein that is generally only found in embryos. Instead of growing tumours as expected the mice grew larger and hairier, and could regrow body parts. Weird though this is, genetic modification could lead to great medical breakthroughs.