If you can convince the mugger to pose like the one in the drawing, including not having a body, you might be OK. But if your enemy gives you unfettered access to their face and you still need extra weapons to win, you're probably screwed. So really, the only way this pad could defend you from attack is if you wrote down your PIN number and handed it over with your wallet.

Revolver Flick-Bayonet

Patent Number: 946,132

In the most tragic firearm-based mistake outside of thinking your gun's unloaded while you clean it with your penis, the cartoonishly-named Henry H. Hull of Ohio designed a revolver with a switchblade. Because after you've pulled a gun on someone, that gun then pulling a knife will be what really scares them. If you've never fired a handgun, attaching extra weight to the end of the barrel is worse for your aim than drinking a bottle of tequila.

Worse, it's not an attachment for existing revolvers. The switchblade is built into a protrusion from the barrel so you have to buy an entire new gun just for this idiotic addition. A gun's entire deal is propelling extremely unfriendly things at your enemies, but it's meant to be bullets by explosions, not a knife by a little spring. It's a worse weapon upgrade than sprinkling sneezing powder on a landmine - there's no conceivable enemy it will be effective against, and there's better than good chance it'll get you killed.