I'm the same as Faithless Cat, I squeeze spots on my arms until I see something come out - be it water, puss, or blood. It sounds gross, but it does give me a high.
I also pick the spots on my face. Even when I'm conscious I'm doing it and I should stop, I carry on picking. I think it's because I don't like it being uneven, and I feel like they are protruding 100 times more than they are.
I pick my scalp as well. Either I pick so much that it bleeds, then it heals, then I pick the scabs, or I just pick and scratch the dandruff (this all sounds really gross, so I'm sorry if I make you cringe or want to throw up)