Found this in a friends sig on SFDC, thought it was pretty funny so I should share it..
“Tamakeri is a recently introduced type of Japanese fetish pornography. Tamakeri means “ball kicking”. A female model kicks a man in the testicles, which sounds and looks quite odd for Western viewers. The “slap’ sound effect that’s raised when a kick lands home is what most of the fans say they like. The main market for tamakeri videos is among masochistic young men for whom the idea of getting their testicles kicked is sexually stimulating, at least in fantasy.”
I’ve actually seen a video clip of this and it does make a slapping sound and it does look VERY painful. Some extreme forms involve stilleto heels and standing on the above mentioned nuts…ooohaaahheeeearrghh
Taken from https://en.wikipedia.org/wiki/Tamakeri