#1 The Montreal Screwjob - WWE Survivor Series 1997

It's impossible to do a list like this without bringing up The Montreal Screwjob. Arguably the most infamous match to ever take place in WWE, Shawn Michaels faced Bret Hart at Survivor Series in 1997.
Hart was on his way out of the company, but was the WWE, then WWF Champion. Vince McMahon had tried to talk Hart into dropping the title to Michaels at Survivor Series. However, The Hitman, after years of bad blood between himself and Michaels, just couldn't do it. He definitely couldn't do it in Montreal of all places.
Hart had promised to come back the next night on RAW to handle it. Whether he'd hand the title over to Vince or drop it to someone else, no one is entirely sure. However, that was the deal that he'd worked out with Vince. That wasn't the plan that the boss wanted to go through with, though.
After all, he'd had his former wrestlers appear on WCW the day after contracts expired with the chance to cut scathing promos on WWE. Notoriously, Medusa had gone to WCW still with the WWF Women's Championship and dumped it into a trash can on screen.
Vince just couldn't trust Bret Hart. It was that simple, and it led to, of course, one of the worst moments in Hart's career. During the match with HBK, Michaels locked Hart in the Sharpshooter. McMahon demanded referee Earl Hebner call for the bell, and he did, claiming that Hart had submitted.
The rest is history. Hart left to join WCW while WWE found their greatest heel in Mr. McMahon.