No, I've never shot anyone - by "shot" I was referring to a punch or kick.
As far as times I've dropped someone with a single clean shot, well, it was usually just a simple clean shot to either the chin or solar plexus. To the chin, usually a roundhouse or a ridgehand or punch. To the solar plexus, either a punch or a front kick. Oh yeah - and I dropped one of our black belts when I was about 15 by an accidental groin stomp - he was trying to sweep my foot out from under me, I pulled my kicking foot straight down, only to feel it hit something squishy. I looked down, I see his eyes as big as saucers, and my foot planted square on his groin. First thought through my head - "Uh oh - I'm dead". Similar stories for the times I've been dropped - a bareknuckle punch or front-round kick to the solar plexus (happened fighting 2-on-1 on my BB test), a punch or roundhouse to the chin, spinning hook kick to the back of the head, etc.
Now that I think about it, most (I'd say 80-90%) of the clean knockdowns I've seen were caused by one of two things - surprise/lack of warm-up (it seems to take time to get up to full speed - catching someone in the first 1-2 seconds before they adjust to the speed of their opponent seems to happen fairly often) or fatigue. Mostly fatigue. Being tired takes the focus out of technique, slows your defense & offense down, makes your breathing outta whack, etc. Whoever wears down first usually loses, all other things being relatively equal.
Weirdest nearly disabling blow I've been hit with was a straight-up (as in vertical - this guy was real flexible and short) side kick to the armpit. It surprised me when my arm went numb, but it's just plain weird being kicked straight up like that - all the weight just comes off your feet - weird. His reaction was funny - "eeeewwwww!" while wiping my armpit sweat off his foot...
LASur5r, I don't know what to say about your story except wow! Did you get off easy! Nowadays, they probably would have shot you & the witnesses just for kicks. Your experience is a good example of how things go when reality rears it's ugly head. You just don't ever know what's next....