The most famous example would be the Montreal Screwjob at Survivor Series 1997, although one half of the people involved (Bret, Patterson) had a planned finish for a DQ and the other half (Vince, Shawn, Earl, HHH) had a completely new plan in mind without telling anyone they were gonna do it. So not sure if you wanna count it or not.
Another famous example is Summerslam 1997 where during the Intercontinental Title match between Stone Cold Steve Austin and Owen Hart, Owen had broken Austin's neck with a Sitout Piledriver, temporarily paralyzing Austin. Owen had to waste time, walking around the ring and trash talk the crowd while Austin was laying on the mat for a couple of minutes and the referee was trying to figure out what to do. Austin could barely move but he managed to roll up Owen with a really weak schoolboy pin to end the match and win the IC Title. It's a shame cause it was a damn good match up until it happened and Austin had to completely change his in ring style after that.
At TNA Victory Road 2011, Sting was scheduled to defend the TNA World Title against Jeff Hardy, but the idiot Hardy showed up at the event, high and in no condition to compete, forcing everyone to rush the match and have Sting beat Jeff quickly in 2 minutes. What an absolute disgrace to the business that was, I was hoping they would fire Jeff after that, it was a big slap in the face to the fans.
Starrcade 1997, where Nick Patrick was supposed to make a fast count for Hogan on Sting, parodying the Montreal Screwjob. Bret, who was the special enforcer or something (I forgot what role he was playing), was then supposed to restart the match and Sting would beat Hogan. Patrick made a normal count, completely screwing up the match and the hottest angle of 1997.
Sid breaking his leg at WCW Sin in a Fatal 4 Way that also involved Scott Steiner, Jeff Jarrett and a Mystery Man. They showed Flair accompanying the Mystery Man to the ring while Sid broke his leg, jumping off the second turnbuckle. The Mystery Man (Animal) jumped into the ring, dropped an elbow on Sid and Scott Steiner covered Sid to retain the belt.
On a house show in 94, The Quebecers were defending the WWF Tag Team Titles against Mabel and Mo, The Quebecers were supposed to retain the titles, but that lard ass Mabel accidentally fell on top of one of The Quebecers and pinned him for the titles. They lost the titles back to The Quebecers at Wrestlemania X.
There's a Youtube video of a Steel Cage match between Bruiser Brody and Lex Luger that took place on a house show where Bruiser Brody starts no selling Luger's punches, Luger and the referee have no idea what's going on, Brody's just standing in the corner, taking the punches without reacting, Luger gives up, climbs out of the cage and abandons the match. I don't really know the story behind it, I think Luger was leaving for another company and the bookers wanted to make him look bad, so they told Brody to no sell Luger's attacks or something.