When I was in middle school some moron decided it would be fun to push me out of a narrow pass between a wall and some bleachers. He did once then decided his friends should see him do it. He was pushing, I wasn't budging, suddenly a forearm slid from my chest up to my neck. He had cut off my airway, and the memory is hazy at this point but I remember starting to pass out (couldn't think, vision going dark, lungs burning the whole nine yards). Luckily someone called out something or other (passing out wasn't really helping my hearing), and the arm released. I fell out of the pass and onto my side, where I then started taking in as much air as possible. I actually didn't want the teachers involved in this, but apparently my classmates decided they were going to anyway. Had to write up a small police report, see the vice principal, and then go back to class. He was suspended and cried as they took him out of the school.
Also almost purposely stabbed myself in the stomach at the age of 8.