Sickle Ring, the ball and chain necklace, and several "Light as a feather. . ." items.
Can you imagine shaking someone's hand with a 4 inch knife covering their knuckles? Or getting into a bar fight, only to find out the person swinging back is Edward Scissorhands. Are rings like this even legal?
What if the love of your life proposed to you with this sort of ring? "Marry me or I kill you". I think my answer would be yes.