It's been quite a while, so I don't remember everything, especially since it was platonic and incidental to the actual activity we were doing. But I remember several times locking one of her legs and tickling her foot to get her to tap. She was stubborn and tough, but much less skilled and mismatched (like I said, I was just helping her get some extra experience in). So being stubborn, with me at least, she would resist tapping, and I wouldn't feel comfortable pressing into pain territory with a girl, so I'd tickle her when it came time to prove to her that she was done for. I don't remember the contexts for this, but I also tickled her underarms and ribs a few different times, but it was mostly the feet because she had extremely strong legs and I usually needed to get control of those quickly.