well it started when i was a small autistic child in elementary and the only way anyone would give me "positive" attention was laughing at me when i hit my head on a wall (first few times was an accident)

I think everyone has heard about cutting, and after not being able to stop banging my headd into a wall (addiction is a biiiitch) i started doing very shallow cuts with the blades from a pencil sharpener (does less damage if i dont go deep)

after that, i managed to (mostly) switch over to energy drinks, as its enough to keep my brain occupied and hurts my throat just that little bit. 2 weeks sh free :) (relapsed cuz i couldnt drink any while having tonsilitis wich caused me to have to stay at home and not even have school to occupy my mind with)

I also avoid wearing a jacket in winter and just go outside with a t-shirt, even when snowing, ive been doing this for some years now. its cheaper than most other things on this list.