In my younger days I took the occasional rabbit and squirrel with my trusty old Whammo wooden slingshot. I still play around with a slingshot, but have upgraded to a WristRocket. I haven't shot at anything alive in years, but can hit cans often enough to have a pretty good chance if needed, as long as I can get in range. Do not plan on using rocks as ammo, unless you can find real round rocks. Most rocks are not areodynamic enough to fly straight. Marbles work really well as ammo, if you can find them in todays world...