I remember one as a kid it was a delayed one, the next day I lost control of all my muscles.
The next one was in training. I was knocked out for at least 4 seconds that I know of.
The effects of this one were more noticeable due to it being in my recent past. I felt a little dizzy, and forgot how to do some of my job, but I recovered within a week I think.
Throughout life there are bumps along the way some may be painful...others not...who gives a damn in the end you'll still die