It's a fine line to cross. Back in college, I was banging this gal, and she dumped me for some pothead. When I stopped by to pick up my stuff, said pothead mouthed off and I gave him a roundhouse kick to the face. It was perfect and the only time all of my martial arts training as a kid paid off, and of course there were no camera phones back then so nobody got a good video of it, which sucks because people think I'm making it up. Anyways, the little shit started crying and talking about how if he had a gun he'd kill me, and he was going to get his buddy's gun and I'd pay for what I did, etc. so I just described in graphic detail the last time I had sex with his girlfriend/my-ex, and then left him crying.
I doubt he had any friends who had guns, and even if he had access to one, I doubt he'd have the balls to confront somebody, but he should be on this list because he was an idiot.
edit: I don't spel so gud.