I've been knocked out. Never passed out for any reason other than alcohol.
I was riding my bike at a "bmx trail" made with plywood, dirt and shovels back in jr. high. I went down a plywood ramp, up a four foot jump and hit the lip wrong.
I'm sure I looked like a tangled mess as I tried to unsuccessfully seperate from the bike and land as gracefully as possible.
The bike and I came down and i hit my head pretty hard. Knocked me out for quite a while I'm told. I had a concussion.
The last thing I remember is riding from my friends house to the field and watching a friend (there were six of us) go through the course.
Supposedly we were there for a couple hours before my accident, but I don't remember any of it, the trip home (helped along by my friends) or the trip to the hospital when I passed out again at home.
I remember the doctor shining a light in my eyes and instructing my parents to wake me me up every 30 minutes for two nights in place of an overnight hospital stay.