I have been made to cum just by being repeatedly hit in the balls. A girlfriend liked to hit me in the balls and I hated it but then I started to love it. She loved it. She also liked to give me handjobs until I was about to cum then stop only to start again. This would continue until I begged to cum. She would let me only if I could take slaps to the balls during and for a little after orgasm. It's strange how you can hate it and love it at the same time.