In Iron Man 3, as the movie nears its climax, the camera briefly cuts to Tony's wrecked home; a hidden underground room was shrouded in complete darkness, until more than a dozen arc reactors start lighting up the place.
Toward the end of Thor: The Dark World, as Thor leaves the throne room, Odin is revealed to be Loki in disguise.
In Captain America: The Winter Soldier, Steve gets into a fight with the titular antagonist and rips his mask off. Cue a shot of the unmasked Winter Soldier looking back at Steve revealing him to be Bucky Barnes.
In Avengers: Age of Ultron, the Avengers are debating whether Vision can be trusted, since he was created by Ultron. Then Vision casually picks up Mjolnir and hands it to Thor.
Earlier, the shot where Ant-Man turns to giant size at the airport (especially since there had been no foreshadowing that he could do this up to this point).
In Guardians of the Galaxy Vol. 2, Nebula and Gamora suddenly realizing the cave they've fallen into is filled with thousands of skeletal remains.
In Spider-Man: Homecoming, Peter Parker rings the doorbell to his date's house on Homecoming night, and Adrian Toomes opens the door, revealing that Peter's crush is the daughter of the film's villain.
In Thor: Ragnarok, Thor throws Mjolnir at Hela in their initial confrontation. Then she not only blocks the hammer with one hand, she then destroys it.
In Avengers: Infinity War, Thanos snaps his fingers with the Gauntlet and one-by-one, heroes and others start turning into dust.
Earlier, when Thanos and Gamora search for the Soul Stone on another world, its hooded guardian steps forward to reveal himself as the Red Skull.
In The Stinger for Ant-Man and the Wasp, Scott is in the Quantum Realm on a mission and calls back to Hank, Janet and Hope but hears only static. Cut to the rooftop where all three are now nothing but ash, the camera focusing on the communicator as Scott's voice calls for help.
The final Once More, with Clarity flashback in Captain Marvel is a Wham Scene, but two shots in particular are notable — first, Carol bleeds from her nose after her plane crashes, and her blood is red, proving she's human, not Kree. Second is when Mar-Vell's killer steps out of the fog, and it's not a Skrull; it's Carol's supposed friend, Yon-Rogg.
The Avengers track down Thanos, swiftly overpower him, and cut off his arm to take the Infinity Gauntlet. To their horror, when Rocket reaches for it, the Infinity Stones are gone.
Some In-Universe, personal ones for Scott, who has just escaped the Quantum Realm and has no idea what has happened to the outside world. He finds a memorial to the victims of the Decimation, which includes his own name. Then he realizes the true nature of the Quantum Realm when he returns home to find his daughter Cassie is now fifteen years old. Later, in a more comical example, it's from his perspective that the audience is introduced to Professor Hulk.
2014 Thanos prepares to kill Thor with his own axe, only to be hit off-balance by Mjolnir. The enchanted hammer then to flies into the hand of its wielder — not Thor himself, but Captain America.
Just as hope is nearly lost and Thanos has Captain America, Thor, and Iron Man backed into a corner, Cap gets a call from Falcon, who tells him to look on his left. He turns to see a magic portal, from which Falcon, Black Panther, Princess Shuri, General Okoye, and the entire Wakandan army emerge. Soon more portals show up and nearly every living hero and ally in the franchise assemble to defeat Thanos and his army.
And then Cap utters the line that every fan had been waiting 10+ years to hear: "Avengers, assemble!". And to make it even better, he did it quietly without histrionics, which made it all the more powerful.
Thanos, now with the completed Infinity Gauntlet, declares himself the winner and snaps his fingers, only to hear a metallic clang. Confused, Thanos looks at his Gauntlet to find it empty and then looks to Tony... who has all six Infinity Stones arranging themselves in a make-shift Infinity Gauntlet from his armor. He then snaps his own Infinity Gauntlet, destroying Thanos and his army at the cost of his own life.
At the end, Sam and Bruce panic when Steve doesn't immediately come back from returning the Infinity Stones. Bucky then points Sam to someone by the side of a lake...who is actually an old Steve.
In Spider-Man: Far From Home, the objects and some of the people in the bar that Peter just walked out of begin to disappear in flashes of blue light...as Mysterio, whom Peter just handed EDITH off to, cracks asinister smile.
The film's stingers also have two huge ones: one from the mid-credits scene (where the news broadcaster cuts to footage from "controversial news website" TheDailyBugle.net to reveal an extremely familiar-lookingJ. Jonah Jameson) and one from the post-credits scene (as "Fury" and "Hill" reveal that they were actually the Skrulls Talos and Soren the entire time).
The first thing we see of Peter's lawyer is a hand on a white cane. The shot pans out to reveal Matt Murdock from the MCU's discontinued Netflix branch, making his way into the canonical MCU mere days after his nemesis the Kingpin did likewise in Hawkeye.
After Ned's wish to see Peter again opens a sling ring portal, he and MJ see Spider-Man in the distance. They call out to him, and as he approaches it slowly becomes clear that he sports the distinctive gigantic eyes of the Webb-verse Spider-Man, who promptly unmasks to reveal the face of Andrew Garfield. A few minutes later, Ned tries again, and the next portal opens to inevitably reveal Raimi-verse Peter Parker.
The mid-credits scene mostly seems like an extended gag... until the final shot, which shows that a spawn of the Venom Symbiote stayed behind... and it starts moving.
Guardians of the Galaxy Vol. 3: Rocket, coming across a cage of younger versions of his species, then looking up to see the cage's label, confirming once and for all he was an Earth Raccoon all along.
In the episode "Turn, Turn, Turn", the signal is finally decrypted and it's not good news: OUT OF THE SHADOWS, INTO THE LIGHT: HYDRA.
In the same episode, Coulson's face changing right after Garrett says something only Coulson knew: "...the same machine she used on that bitch in the flower dress."
Used in the episode "Shadows" when it turns out Simmons isn't really there and Fitz is talking to himself.
At the end of the first episode, it is shown that someone in a S.W.O.R.D facility is watching the "Sitcom".
After running into the Beekeeper, Wanda calmly rewinds time so that she and Vision never left the house.
After she hurls Monica out of WestView, Wanda briefly turns around to see Vision's corpse.
Before Wanda and Vision can get into a fight, someone's knocking at the door. Wanda opens it to find that it's Pietro. Oh, but it's not just any Pietro: it’s the version of Pietro played byEvan Peters.
Wanda, after feeling that Vision has escaped from Westview, freezes everyone in place and extends the barrier of the Hex beyond the limits.
Wanda heads down to Agnes' basement to look for the twins, and comes across some sinister-looking altar. Then enters Agnes, revealing that she too has magic.
In a mid-credits scene, Monica tries to break into the basement only for her to fall under Agatha's spell, with "Pietro" appearing behind her.
"Pietro": Snoopers gonna snoop.
In a flashback, Wanda- after being allowed to examined Vision's corpse by S.W.O.R.D.- drives to the real Westview, and in a moment of sorrow, creates the Hex and "Vision".
During the battle against Agatha, Wanda fully embraces her destiny as the Scarlet Witch and creates a new costume for herself.
In a mid-credits scene, Monica is told to meet with a S.W.O.R.D agent (who is revealed to have been a Skrull the entire time), who has a message from a friend that’s heavily implied to be Nick Fury.
In a post-credits scene, Wanda is shown living peacefully in seclusion in a cottage, until an astral form of her dressed in her Scarlet Witch outfit is seen in the back room studying the Darkhold, and she hears her children crying out for her.
After handing over the shield to the "Captain America Museum", Sam (and Bucky) are horrified to find someone else announced as the "New Captain America".
John Walker, in a very un-Steve like move, pulling a gun out in the middle of combat.
The revelation of Isaiah Bradley, a Black Super-Soldier that had been dosed during the Korean War, then later imprisoned and continually experimented on by the American Government after Steve was frozen in the iceberg.
Then there is the revelation that there are still 12 vials of the Super Soldier Serum out in the world.
After saying goodbye to Sam and Bucky, Sharon gets into an undisclosed car, informing the driver there has been a problem.
Bucky tells Sam and Zemo he needs to take a walk to clear his head, and runs into Ayo, demanding he surrender Zemo over to Wakanda.
John Walker nonchalantly standing with Captain America's shield, stained with the blood of a Flag Smasher he just bludgeoned to death in broad daylight.
An in-universe example: after Casey gives Loki the Tessaract upon threat of death, Loki's gaze wanders to the open desk drawer it was previously stashed in, only to freeze... because he sees dozens of Infinity Stones just laying there. Casey casually tells him that they get a lot of those, and some of the guys even use them as paperweights, indicating that the TVA is on an entirely different level note While Infinity Stones are useless in the TVA realm, the TVA members get them by handling Variants wielding active Infinity Stones, with all the power that implies. and Loki is utterly stunned.
Sylvie killing He Who Remains, then watching in horror as the Sacred Timeline begins to splinter.
At the end of the first season finale, Loki finds himself back in the TVA and immediately runs to find Mobius and B-15 to let them know what has happened. Then he discovers that not only do they not remember him, but the statues of the three Time Keepers have been replaced by a single statue of a variant of He Who Remains, implied to be Kang the Conqueror.
Timely going to repair the Loom, only for the temporal radiation to spaghettify him, leaving the team helpless as the Loom explodes, with a close up of Loki's terrified eyes as he and the rest of the TVA are hit by the ensuing blast.
