I had a girlfriend in college who was into some kinky sex. We were both bisexual, so that opened up a lot of options.

We had a threesome where I sucked off a male friend while fucking her. That totally made her hot, she loved seeing me swallow his load.

We had another threesome where she played around with a girl friend of hers while I fucked her, but the other girl wouldn't let me touch her. Too bad.

Various times we'd have sex and let friends watch, up to 3 or 4 people watching while we put on a show. Videotaped it too.

The wildest things we did were at an adult theater. We'd go there sometimes and have sex in an arcade booth, while guys would watch us through the glory holes on each side. They'd reach through the holes and fondle her, finger her pussy, play with and suck my dick. Then she'd get on her knees and I'd cum in her mouth and on her breasts. She loved it as much as I did, we went on many occasions.