(SELF HARM TRIGGER WARNING)
I once gave myself a tattoo for the purpose of self harm. I was feeling very numb and wanted that pain and rush that cutting gives me but didn't want to cut myself as I was doing very well with not doing that so I gave myself a tattoo instead to feel the pain. It worked pretty well although that was two years ago so it's pretty faded now.
I don't know if you've ever seen the show House of Cards but one of the characters (Jackie Sharp) gets a tattoo (a big one done in multiple sessions) because she was in the army and the pain of the tattoo makes her feel better about having killed so many people. I guess that could be a form of self harm.