one time my friend showed me the bruises that nearly completely covered her breasts after a marathon fuck sesh with one of her many suitors. it was scary. i'm all about a little nipple pinching, especially right before climax, or when you're getting fucked like a champ and he reaches around to pinch them...mmm. nibbling, too, even til it hurts JUST a little. but after maybe a 3 on the breast pain threshold i'm all set.