My sister's right butt cheek, with a bb gun at about 250 yards. Had the thing propped on my thigh at about a 45 degree angle and just figured I would hit the barn roof near her. Mom hit me so hard that I don't remember the next three days.
The best shot was sighting in my brand new .22 on Christmas Day though. Dad and I were out in the pasture shooting at the target about 50 yards away. Dad figured he had the thing sighted in since I was pretty much hitting were I was aiming. I said, "Daddy, I think I can hit the thumbtack holding the target up." "you can't hit the tack. I can't even see it."
Bang!
"ok Son, I think you've got the idea. It's cold. Let's go in."
Still don't know who was more surprised that I got it.