I remember when I was a kid, one of us figured out a way to get a weird hypoxic buzz. You'd do 5 or 6 rapid toe touches and then stand up straight and squeeze your neck. I stopped doing it after I fell over backwards once and almost killed myself by smacking my head on a glass door.

The best nitrous high I ever got was in the dentist's office. He left me waiting forever with the nitrous mask on and I reached back and cranked the N lever. It soon felt like I was levitating above my own body in the exam chair. Then I started to pass out, so I took the mask off before I turned blue or something.