Let's say you can choose to give or receive any wedgie you want, no matter how extreme or unrealistic, and you get to experience that with zero consequences. So you can't be injured, no cuts, bruises, chafing, anything like that once its over, you're totally safe, everyone else will also be safe will forget it happened the very next day (should you choose to involve others and assuming you want them to forget)...
What are you going for?
I'll start: I'd want to spend an hour or two with the wedgiesaurus. Yes, I know it's a super cliché thing to pick in the community, but the idea of a creature whose sole purpose is giving absolutely insane wedgies that defy the laws of physics has stayed with me ever since I first saw that scene, and I can't help but wonder what it would be like