Never knocked out by a punch, but got a concussion once.
Long story short, me and my friends got surrounded by a bunch of guys. I told them "No matter what happens don't run away" So of course, they ran away. So eventually I had to as well.
Someone grabbed my collar from behind and my head slammed against the cement. Then I had several guys kicking me until I woke up.
One guy yelled "I think he's dead". And they all ran away.
I was in a complete daze for about 3 days. I remember getting home and throwing up even though I wasn't drunk. I didn't know how to explain it. I felt completely out of it, like I was on drugs, but in a terrible way. I thought it wouldn't end and it freaked me out. I thought the rest of my life would be a constant haze.
Luckily the fog eventually lifted and I got back to my old self. But at the time it was terrifying, not knowing if it would end.
Look. It's a post.