Especially young boy balls. I got it first time from my older brother when I was 14. He always said the same: That's what the balls are for, just take the pain boy!
Never offered my balls to a guy to squeeze and slap, so far, but your invitation makes the thought so much more exciting. I have played NutBall a couple of times and always lost. The more I think about your offer, the more I feel that I want the experience