Girls, plz help me out with this!?

sorry this is so random. i'm 13 and my 14 y.o. brother punched me HARD in the boob today. it's not the first time he's done it, and in the past my mom's grounded him for it. this time, though, she said she would take away his iPod for one day OR i could hit him in the balls. it's my choice. i'm leaning toward the balls thing, but i don't know how to position him (it won't be a sneak attack, he's just gotta take it - standing up, kneeling, etc.). so what are ur ideas for that? i don't want his hands in the way either. lol. help me out, girls!!!