I want one just so that when the shitloads of muggers living around my college finally try to mug me, I can just deploy the hidden blade and say "Yeah, you still want to try that, mate?". My guess is that, even if they could still probably overpower me, they'd be so shocked that they would back down. Additionally, it gives off a "Don't fuck with me" vibe, no?
Yeah, it's probably illegal, and yeah, the chance for misfire is high, but I really want to scare these bastards. They pistol-whipped my former roommate and he had to go to the emergency room. Not cool.