Many years ago, I was in Atlanta for a few months of work. While I was there a friend was telling a group of us that she had a rape fetish. She was complaining that all the porns were all too unrealistic and not focusing on the parts that turned her on.
I told her we would figure something out for her. Just to always be ready, we would not warn her. And that the safe word was ROBOT. Not sure how serious she took it but she seemed to enjoy the idea.