I enjoy some very-light CBT, but I have been with a few guys that were into various degrees of CBT.
My favorite fuckbuddy loved having his balls pulled on, yanked hard. Or he loved it when I put both of his balls into my mouth and pulled on them as hard as I could. We had one session where I sucked on his balls, pulling on them really hard using only my mouth while he jacked off. He was so much fun, but sadly I just found out he moved away last week.
Another guy said he would not be able to get off unless you were pulling as hard as you could on his balls. I found out that wasn't actually true, I had to pull on them way beyond what I thought was okay and then I was lightly tapping on his balls with my thumb. This finally drove him over the edge and he was able to cum.
But the one I always remember was the older guy who I often saw at the adult bookstore. He would go into a booth, drop his pants and jack off. He had a nice dick, between 7" and 8" and a nice thickness. But he was only into twinks, so he was never interested into me. But that changed one day when he had been there for a few hours and there had been no twinks. He came into the booth next to me and let me suck his dick. He then told me to come over to his side. When I got there, he told me that he was into having his balls abused. At first it started with pulling on them really hard. But then it was pulling on them and then slapping them. Eventually, I was hitting them pretty hard. It was interesting to see him take so much pain to his balls. The harder I hit his balls, the more it excited him. At the end, I was pulling his balls down really far and hitting them with the other hand. He finally came. The next time I saw him at the adult bookstores, he was still doing the "twinks only" game to the other guys, but when he would see me, we would go into a booth and I would abuse his balls.