Not quite what I was looking for but it's the best I can find right now...
http://abcnews.go.com/US/Story?id=662272&page=1
I'm pretty sure I read somewhere that certain states allowed feral cat hunting. Of course it would only be allowed in areas that allowed you to fire a gun and hunt. You couldn't sit on your porch in a city and pick off cats. (unfortunately)
I'm not sure what you mean as far as being charged for discharging a firearm. Are you talking about anywhere, or just within a city? I have many friends that own houses on land that you can fire a gun on. As long as you are far enough away from other houses and roads, you are free to blast away!