I think I've shared this one before, but it was old WoD Mage, one of the characters was built like a grizzly bear and dumber than a sack of d10s. He had Strength as a legendary attribute, and elected to make it so that he could deal lethal damage with unarmed attacks.

At one point, the party was attacked by a giant mutant dog which managed to bite onto his arm, just latched right onto it and wouldn't let go. So, he decides he's going to punch it in the head, and use Forces magic to make it a super punch! Does great on his Arete roll, getting a bunch of extra dice to his damage - unfortunately, he botches his subsequent attack roll.

As a result, he managed to punch his own arm clean off his torso. The dog ran away, arm still in its mouth, and the party had to split up, half staying behind to stabilize the big dope, the other to chase after the dog and try to save the arm so they could re-attach it.