One of my friends has taken a Pedigree in a real fight. It knocked him out, too. Instead of his head / torso hitting the floor, his head slammed into the guy's knee, so it was a kind of Pedigree / GTS combo. It was all over after that We still take the piss about it to this day, as a Pedigree is a pretty ridiculous move to take in a fight.
Dude does it think he's going to completely KO his friend (which he could) but doesn't realise that when Taker/Kane do it, the impact is non-existence for the person taking it as they leave space for the head not to connect the mat. So the dude does it and ends up in agony as it's his knees that get fucked.
Minor note but remembered that Flair had headaches after his match with Taker at WM18 because he did end up hitting the mat after the Tombstone.