Received is about 9 years ago when my buddy showed me that my armour shifts sometimes, and hit me in the 1 sqin spot right above my right sciatic nerve via a fendente to backedge return on the pass. It lit me up bad. My world went white, I dropped like a strings cut marionette, and thought "Don't puke, just don't puke out of your helm. It'll look bad". It cause piriformis to spasm on my Sciatic that had just been hit. I've broken bones, dislocated ribs, and taken crotch shots that hurt less. Heck the injury still hurts.
Given is a tie between breaking Michael-Forrest's pinky five years ago via a fendente from a high guard (have vid). It wasn't terribly powerful but he executed a counter badly while still basically out of range. See I was trying to get him to bite on a fake so I could gig him. Guess it worked.
The other is a story from about 10 yrs ago in the SCA.
On his last practice, and last fight, before going off to China Lake to do his dream job, a newly authorized fighter came against me. I threw a shot for his gut. I was guiding off his shield, he lowered it to block and I lowered to continue the strike. When it landed it was N.B.C. "Nothin' But Cup" with some 8 inches left in the thrust. He teleported to his knees some 4 ft away. I said " I didn't?!" in a high voice he say's "You did!". Lovely present to send him off with.