Girls, hey, please give me some help :)?

sorry this is so random. i'm 13 and my mom is letting me choose the punishment for my 14-year-old brother, who punched me HARD in the boob today. it's not the first time he's done it, and in the past she's grounded him and stuff like that. this time, though, she said she would take away his iPod for one day OR i could hit him in the balls. what do you think? my sister said i should go for the balls, but i don't know how to position him (it won't be a sneak attack, he's gotta just take it standing up, kneeling, etc.). so what are ur ideas? lol. help me out, girls!!! how would u do it?