Someone mentioned earlier having a lover piss on their ass. I've done this in private and really enjoy it--I've been both the pisser and the pissee. :-) It's always been in the shower, so it's not really humiliating or dirty for us. It just feels warm and very intimate, and playful, like kids who aren't shy about using the toilet in front of each other.

My favorite little humiliation is having my bf come on my breasts. We did this just today in the shower--I knelt down and jacked him off onto my soapy chest. It's not genuinely humiliating, it just feels like kind of a dirty, slutty thing to do. Right up my alley!