Lol. I think I'm the freak here because so many of these things I love and would do again and again. But PTA sounds like pure hell. My sister is the type that loves it which means it's definitely not for me (not that I have or want children).
Riding a horse on a hilly trail. My family loved it and I was terrified the entire time. I'd maybe ride again on a flat surface but never again on hills!
I went to one of those airsoft gun places where people run around simulating a battle or whatever. It was horrible. Those things hurt more than you'd think and the whole scenario was scary. Never again.
I would say skiing, but if I got lessons I would be open to trying again. Given my age and level of interest I doubt that will ever happen though.