No, I would never use a gun, nor would I lower myself to an enemy's level and use any kind of violence. You can't hate someone for doing something you then go out and do yourself! It makes you no better than them. There are better ways to deal with such people, legal ways and less violent ways.
War is a different matter though. I would be totally useless as a soldier I'm afraid, as there is no way I could use a gun or any other weapon on someone. But I do have great respect for soldiers, who risk their lives for their country. No respect for the governments though that sacrifice their lives with such ease in countries we have no business being in.