DM is me. I've got a barbarian player who likes the tactic of tearing out an opponent's throat with his teeth, a la Fyodor vs. Quaggoth in Daughter of the Drow. I rule that he has no bite attack, but neither does a vampire and they can drain blood with a pin, so I require a pin. No problem for a burly barbarian, really. so I require one more grapple check to make the attack, and . . . shite then what? He can't just auto-kill with his mouth. Pinned grapplers aren't helpless so no CDG, but what? Do I let him roll damage? What do I do that doesn't involve just saying "No, you can't because I say"
P.S. The wacko has Magic Fang permanencied on his teeth.