When I was about 10, my Brother and I each got a "Wrist-Rocket" style slingshot for christmas.
The first few months were spent shooting at normal stuff- passing trains, kids on bicycles a couple streets away, rabbits, the neighbors cats, streetlights when we snuck into town in the middle of the night, stuff like that.
About 9-10 months later, we were in the yard raking leaves for our allowances, and one of us got the bright idea to shoot the other with a slingshot, and an acorn. He hit me in the arm, I grabbed an acorn, pulled up and released lower than I had intended. I shot my brother in the nuts with an acorn. He fell over and threw up.