We used to say the Marines taught us just about enough hand-to-hand stuff to get ourselves into trouble, but not quite enough to get us back out.
The Instructor wanted the biggest, baddest 'Cruit we had, and had to settle for the biggest; me. I was 19, 6' 5 1/2", and all of 160lb wringing wet. I was supposed to throw a right at him, but I figured the only way I was going to get anything out of this was to cross him up and threw a left.
About two minutes later, as I was waking back up; I heard somebody yell, "Call off the ambulance, he's coming back around...". I remember my head hitting the mat, hearing him count "1..., 2...,3..."; and then nothing.
The experience of a lifetime, and first proof positive of my own mortality.
Greg