Gruesome Finish( Exemplars of Evil, p. 24)
You deliver a terrifying blow to finish off a victim and strike fear into the hearts of your enemies.
Base attack bonus +6,
Whenever you make a full attack and reduce an opponent to 0 or fewer hit points, you can give up any remaining attacks you have in the round to force the target to make a Fortitude save (DC 10 + 1/2 your level + your Cha modifier). If the target fails the save, he dies instead of becoming disabled, and all creatures within 30 feet must succeed on Will saves against the same DC or become sickened for 1 round.
You can use this feat only if you have still have one or more attacks left in a round after reducing your target to 0 or fewer hit points.