A kink post on tumblr mentioned figging which is a kink where you peel and carve a piece of raw ginger root into a buttplug shape and then slide it into your ass. The ginger is hell on sensitive membranes but doesn't do damage to your skin so you can experiment with pain without bruises or chemicals that mess with your nerves (like icy-hot which is apparently very bad for mucous membranes). It made me whine and squirm and I just barely made it the five minutes I set for myself as a challenge.