"Black Saturday". In 1984, the then-burgeoning WWF had purchased Georgia Championship Wrestling, a popular yet struggling Southern-style promotion. Vince McMahon appeared in the opening segment of the July 14 edition of World Championship Wrestling, GCW's flagship nationally televised program, to deliver a show that mostly had material that had ran already run on other WWF programs. Complaints from the GCW fanbase lead TBS to give Bill Watts and Ole Anderson's promotions slots on their schedule in tandem with WCW, and the WWF was ultimately forced to sell the TBS timeslot to Jim Crockett, whose promotion would become WCW.
The 05/27/96 episode of WCW Monday Nitro featured the shocking return of Scott Hall and the beginning of a landmark storyline in the industry, one that would effectively swing the balance of power towards WCW (legitimizing the company in the eyes of the mainstream public) and keep it there until WWE came back with a vengeance a couple of years later.
The 07/29/96 episode of WCW Monday Nitro opens with the great announcement, tonight we have two title matches: The Giant and Arn Anderson for the WCW World Heavyweight Championship and Rey Mysterio Jr. and Eddie Guerrero for the Cruiserweight Title. That alone is awesome, but after the opening match Ric Flair's theme starts and it's Ric Flair and two of the Four Horseman against Sting, Macho Man and Lex Luger. Man, this show is going to be awesome. I mean, seriously SERIOUSLY awesome. In the middle of the match Stinger is getting the crap beaten out of him, and it's looking like it could be comeback time. But then Jimmy Hart runs into the arena screaming "Get back stage!" and we find Scott Hall and Kevin Nash tearing shit up and beating Arn Anderson and Marcus "Buff" Bagwell up with baseball bats. Then Rey Mysterio comes in only to get picked up and thrown into the side of a trailer HEAD FIRST and lies on the concrete motionless. EVERYBODY runs backstage and there is chaos, wrestlers in agony and people screaming for help. Then it hits you: there are going to be no title matches tonight. The nWo have hospitalized the competitors. Everything is ruined and the entire show is thrown into chaos. Bobby Heenan doesn't feel safe and walks out on the commentary team. Before this the nWo were nothing but Hulk Hogan and his buddies talking shit and pulling silly stunts. This episode, shit got real.
Uncensored 1997. The nWo win the main event match and what amounts to basically a perpetual "Money in the Bank"-type clause for all WCW titles. The REAL development, however, is Sting ending months of speculation on whose side is he on by kicking the nWo's collective asses, striking the first real blow against the renegade group.
The 04/13/98 episode of Raw had the company teasing a match between "Stone Cold" Steve Austin and Vince McMahon, leading to the creation of their own Wham storyline which not only broke WCW's 84-week-long winning streak in the ratings war and swung the momentum right back in the WWE's favor, but kept it there permanently after WCW went bust.
The 03/26/01 episodes of WCW Monday Nitro and Raw, in which the last Nitro segment ever was a Raw simulcast. Nitro and Raw both opened with Vince McMahon gloating about his purchase of WCW. WCW was known to be in financial turmoil at the time and there were (mostly unsubstantiated) rumors that McMahon was working to purchase it, but the deal was only announced the weekend before the broadcast. The simulcast segment also culminated in a huge (kayfabe) swerve involving Shane McMahon, as if Vince McMahon buying out his bitter rival wasn't huge enough for one night. To say nothing was the same in pro wrestling after this night would be a dreadful understatement.
And then a few months later, when ECW showed up...
WrestleMania XXX, April 6, 2014, is the day Brock LesnarendedThe Undertaker's two-decade long undefeated streak. Not to mention Daniel Bryan's WWE World Heavyweight championship win, which many will argue served as WWE's admission that he has taken the place of John Cena (who wrestled essentially a midcard match, not for a top title, for the first time since his Wrestlemania debut ten years ago) as the company's top face.
June 2, 2014. The RAW after Payback, after The Shield having defeated Evolution once again. But then come the main event that was going to be Randy Orton vs Roman Reigns. However, Seth Rollins wails on Dean Ambrose and Reigns with a steel chair and sides with Evolution.
August 29, 2016. A Fatal Four-Way No DQ Elimination match on Raw to determine the new Universal Champion is held between Seth Rollins, Roman Reigns, Kevin Owens. and Big Cass. Cass gets eliminated in short order, and when Rollins and Reigns spill to the outside, here comes Triple H, who plants Reigns with a Pedigree and has Rollins eliminate him. Then he turns towards Owens...and then spins around and pedigrees Rollins, giving Owens the Universal Championship and anointing Owens as the new face of RAW.
WrestleMania XXXIII: After losing to Roman Reigns, The Undertaker leaves his hat, gloves, and coat folded up in the middle of the ring, a non-verbal announcement of his retirement.