a guy kicks (punches, knees, squeezes) another guy more or less gently in his nuts ^^
Ballbusting (not found on this website except some links in the link
section): a girl does the above to a guy
(m/f ballbusting doesn't make sense for obvious reasons :-)
a guy dominates another guy with his feet, e.g. presses them in the
other guy's face, rubs them on the other's nose, etc.