The key thing is a horrible idea. You're going to likely end up hurting yourself, and unless you have the grip very tight, its not going to pierce.Keys, and a pen. Put a car key between two of your fingers and punch with that, you could punch anywear and really hurt someone. Pen is the same, hold it in your hammer fist and just stab like crazy. I've used the pen before and believe me, it stopped the attack. Best part is, keys and a pen are allowed everywhere.