I’ve had fantasies about dating a woman who turns out to have a collection of venomous snakes, and one night, after I’m already chained down to her bed, she milks the venom from one of her snakes, loads it into a hypodermic needle and injects the venom directly into each testicle. Certain types of snake venom actually digest the tissue in the immediate area of the bite, so my balls (and eventually my the root of my cock) would be slowly digested while still attached. After a few hours of that, she could easily pop both testicles with a gentle squeeze and rip off my entire cock with a hard tug.