#2. Brock Lesnar lands on his head at WWE WrestleMania XIX

Brock Lesnar is, without question, WWE's gruff, lumberjack-looking, MMA-fighting Mayor of Suplex City - and one of the biggest draws in WWE's history. He's got his ring style down pat, knows exactly what he's doing, and is efficient and destructive when he goes to work.
Lesnar has headlined plenty of WrestleManias, but during his very first - WrestleMania XIX - he was a completely different wrestler. Make no mistake, he was still awesome - you don't get to headline WrestleMania if you're not awesome or Lawrence Taylor. But this was early in his career and Lesnar was still trying to figure out his style.
At WrestleMania XIX, Lesnar faced then-WWE Champion Kurt Angle in the main event. It was a great match from start to finish, but at one point near the end, Lesnar decided to head to the top rope and attempt a Shooting Star Press.
You can probably guess by the title of this entry how that turned out. (Warning: the following video will probably make you flinch.)
Thankfully, this is Brock Lesnar we're talking about, and the Beast didn't suffer any serious damage from the mistimed landing. It was still a pretty scary moment, though - just look back at the previously mentioned Steve Austin incident.
Brock would go on to defeat Angle and win his second WWE Championship.
Lesnar would leave WWE a year later and go on to have a historic career in UFC. He would draw upon that experience upon his return seven years later with a more grounded, less risky style.