Here's the one that comes to my mind: I've seen a number of gun tats that look like the guy with the tat has a gun stuck in his waistband. This has always struck me as a monumentally bad idea. I think it's a good way to get shot for no good reason. (Not that I'm convinced there are very many good reasons to get shot.)
Other than that, a "2A" in a cool design might not be bad. As others have noted though, try to look ahead 20 years and think about what the tattoo will look like. Once that big, bad eagle begins to look more like a cross between an ostrich and a owl, it might not be so cool.
A gunfight is not the time to learn new skills.
If you ever have a real need for more than a couple of magazines, your problem is not a shortage of magazines. It's a shortage of people on your side of the argument. -- Art Eatman