"Realistic" depends a lot on what your willing to do. I'll put a few out here for discussion. I'm not sure how many will be in-bounds for you.
- Nyotaimori night. You will serve as his dinner plate. Normally done with sushi. Oh, he can use your pussy for dipping sauce.
I've done this with my wife before, using fruit whipped cream and chocolate. Lots of fun.
- One days use as a urinal. You will accept and swallow his urine for one day. You gave me the idea when you said something gross.
- One free blowjob anytime / anywhere. You have to trust he will not do this someplace you wouldn't want to do it.
- Go for a ride wearing only a coat, this is your chance to try being an exhibitionist. My suggestion would be to get on the interstate and try to flash a few truckers. It's fun and anonymous.
- Adult store visit, if your as shy as it sounds this will be a big humiliation to you. During the visit you must interact with a staff member (ask a question about a toy). I know this one only works if you leave the house.