I cant vouch for this personally, but it's just something I heard somewhere, although not from anyone in TMF. I once heard of a woman who wrote to a sex therapist, because her vagina was so ticklish, that she couldnt have sex with her husband. The lady said that every time the husband penetrated her for intercourse, she began to squeal hysterically and go nuts, and it felt like tickle torture, making it impossible for the couple to complete intercourse. I cant recall what the therapist said, or how the issue was resolved, but this is the strangest tickle spot I've ever heard. Oh, I'm certain there are women with ticklish vaginas, but except for that case, I never heard of anyone being ticklish to such an extreme down there where intercourse was almost ticklishly painful. So, that's my contribution for strangest tickle spot, only from a story I heard. As for personal experience, I've never encountered or tickled anyone or even talked to anyone, on TMF or otherwise with what I've found to be a "strange" tickle spot. Most I've encountered have tradtional tickle spots. Soles of feet, toes, sides, belly, pits, ribs, etc. This lady I heard about was to me the strangest tickle spot I'd ever heard of, although I'm sure she's not the only one to have that tickle spot.
Mitch