Something that fetishists are into is tickling. Some focus on the feet, others are the full body variety. A bit of tickling can be fun, but when you have the other person tied up and they cannot escape, then it can move over into the torture area. I recall hearing about a guy that called a couple of girls for a two girl call and one would be tied spread eagle to a pool table and the other girl would be tickled mercilessly.
Now it amused me for a couple of reasons, on a two girl call the girls are not in the same room, they are many miles away, yet the caller somehow thought this was in the same room. Some actually have stockades where the person is fully restrained with no chance of escape. You really couldn’t escape and would be at their mercy, squirming likely until you were crying and they teased and tormented you. If you allow yourself to be tied up and restrained, you’re kind of consenting to be tormented to the point of tears, which some are absolutely comfortable with.
It takes a real sub to allow themselves to be handled in such a manner. The surrendering of control to your Master, your Dom, for his amusement and use. Many would have a safe word for when they have truly had enough. Some however may be ball gagged so they really couldn’t say when they’ve had enough. No one can die from being tickled to death, this is true, but it could make for a darned unpleasant session to be in this state for long.