More than likely in you state if you used a shotgun with rock salt or a bow, you are going to either prison or juvie depending on your age. You would be using a lethal weapon to retaliate against eggs and paintballs.

Personally, I would find out who was doing it and then retaliate against their parents cars and homes. I would leave a type message with something like "Do unto others as you would have done unto you and since your son already has..."

If my car got egged and there was a note like that, my boy would have a lot of questions to answer.