Ok. I think this is pretty similar to the "default" idea of "I'm your fucktoy," but I like that, so I voted for the top option.
Maybe this is splitting hairs, but I picture it as their body is yours to do whatever you want with, whenever it fancies you. They may be into it, annoyed by it, unaware of it, completely indifferent to it, but regardless they are unable to do anything about it. Fucktoy implies some degree of enthusiasm, methinks.
When done right I think it's suuuuper hot but my brain isn't always able to pick up on the MC carrier wave of a given situation, which can limit its ultimate appeal. That's kinda on me though.