This is a question I've been asking myself. Since I'm just starting out I only know what I've done. Restraint (bound/unbound) spanking, biting, rough sex, breast play and orgasm (forced/denial).
I'm willing to do more.
I draw the line at any kind of body modification and I don't want any kind of permanent marks. I like my body the way it is.
Sometimes, I wish I was an evil genius. Maybe a little taller, too.