My cat bites my nipples.
Whenever I sit down on my bed and try to read a book, my cat jumps on me and bites me as hard as she possibly can, while yowling and growling extremely loudly. She also kneads me with her claws out as she does this. It causes me a great deal of pain, and I literally have to pry her jaws open with my fingers in order for her to let go... but if I'm not quick enough, she'll just go right back! This is a ritual that happens every night, just about.
Lately she's moved from my arms and my neck... to my nipples. And it feels strangely good for some reason, despite the pain, but I still kick her off because it feels too weird to just let your cat bite your nipples like that.