I messed around with a guy who was into that. I'd never really thought it would be much fun, but I got intrigued when he brought it up and would up spending a fun evening kicking his nuts, kneeing his nuts, squeezing and punching his nuts.
He wound up cumming very suddenly, this all made him so hot. After I'd nailed his nuts one more time, he just threw his head back, grabbed his cock, pulled on it a couple times. And shot a huge load.
Then I stroked off all over his face.