@sozobe,
You might try hitting some things with that keys-in-fist idea.
Try something soft like a pillow first, then something harder--sofa cushion--old used mattress,,,,,,,,
I say this because someone I know tried it on a mugger and it worked, but the big key on the end pinched the hell out of her ring finger.
She says "Good luck ....
Joe(....and go for the eyes.")Nation