It is fun to think about as a fantasy, but I've never found someone who wanted to do this with me, and I'm not sure how I'd handle the reality of it. It seems like something you need to gradually work up to, and where all involved need to make safety and consent a priority.
I like the idea of the contrast it can offer while playing with others. For example, maybe I'm "******" to watch "my" woman getting it from her lover, and one of her girlfriends is dominating me. While the lover is enjoying the pleasures that I am denied, I must endure pain for their entertainment/enhancement. His balls get kissed, my balls get kicked... His pleasure makes her moan, my pain makes her laugh.
I also enjoy the idea of her using an electro-shock collar around my balls, with a remote, and giving me a shock each time her lover gives her an orgasm. The idea that the thing you want most is to see her pleasure, but that there is a consequence you will experience. Maybe she adjusts the intensity on the remote based on her experience, or turns it up so that while he is experiencing a mind-blowing orgasm, you're experiencing the opposite.
Fantasy & reality are often not the same, and finding people who want to try combining the two is often not easy.