(Disclaimer: Solo male cbt) I (m23) bought a tens unit a while back, and one day, I had the idea to use the tens unit on my testicles to shock/electrocute them. I took the tens unit out, got the pads ready, and wrapped a rope/string around my scrotum until they were stretched, tight, and trapped. I put one pad on each ball and turned the tens unit on. I only went to level 4 at first, and it felt kind of nice, but a bit of a zap. I turned it up to 6, and my balls were in a good amount of pain. 7, it was very painful. It felt like someone was squeezing them and shockink them at the same time. I turned it to 8 and instantly felt a deep pain in my stomach and like my balls were cramping. I had to turn it back down right away. After a while, the pads fell off from sweat, and I had to keep putting them back on. At one point, though, I put them back on, and instantly, my nerves/cords on the top of my testicles felt like they were being twisted, pulled, and squeezed all at the same time. There was also an insane cramping feeling in them, along with the timed zaps. It was some of the worst ball pain I've ever felt. Definitely top 3. I had to instantly turn it off. What had happened was, the main part where the electricity came in was sitting on my nerve endings/cords where they connect to my testicles, so instead of the electricity going into my balls and being distributed, it was going directly into the nerves first. (That's also one of the most painful and sensitive spots on the testicles) I've zapped my balls a few more times since then and have been able to go to level 12 and withstand it for a bit. I also put it on my glans/cock head and cock, and its extremely sensitive/uncomfortable, and painful. Its hard to describe, other than it feels like post orgasm when the head is super sensitive and you keep stimulating it, along with a shocking feeling.
I'd love to have a woman sit on my face and control the tens unit, zapping my balls however she wants, and even better if I'm tied up, so I can't escape/stop her.