Batman: Arkham City had a teaser trailer where players get to learn about Hugo Strange. The quality of the graphics is better than the game itself.
Batman: Arkham Origins had an announcement trailer where Batman gets to fight Deathstroke but is interrupted by Deadshot.
Batman: Arkham Knight had an announcement teaser where Thomas Wayne's speech is heard about his passing of his gifts to Bruce.
Destroy All Humans!
Destroy All Humans! 2 had a teaser trailer that shows what the U.S., Russia, Tokyo and London were afraid of. It closes to a shot of Crypto using a peace sign.
Destroy All Humans!: Path of the Furon had a scene in the trailer where Crypto points his gun at the camera and says "How's this for destiny?"
Destroy All Humans! (the 2020 remake) had a trailer where Crypto hypnotizes an American city to "Ich Will" before he vaporizes them. Since it is a Shot-for-Shot Remake of the 2005 classic, it obviously never appears in the game.
Halo 2 had a teaser trailer where John-117 goes into space from the station. In the final game, he delivers a Covenant bomb.
Halo 3 had a teaser trailer where John-117 attacks the Covenant on a blue field.
Halo: Reach had an announcement trailer where Reach has seen it's first glassing with people worried.
Jak II: Renegade has three advertisements showing tourists entering Haven City, encountering Metal Heads and Baron Praxis and a test of the Peace Maker.
Jak 3: Wastelander has two advertisements that promise they "won't end like this". For one of them, Daxter says "I am your father" to Jak, to the latter's confusion. This was made to hide that Damas is Jak's true father.
Perhaps the most shocking example of this trope in the video game medium was its use in Metal Gear Solid 2. It was advertised as mostly straight-forward sequel starring Solid Snake, barely featuring the real main character—a rookie named Raiden—at all. Most of the footage came from the game's intro level, where you do play as Solid Snake, but two scenes from Raiden's portion involving a cyborg ninja and a Harrier attack on the George Washington Bridge were specifically recreated in the intro's location for the trailer. Unlike many other examples, this one earned the ire of many fans. It's also a rare example of this trope being used for aesthetic rather than marketing effect.
Metal Gear Solid V: The Phantom Pain had several sequences from the trailer that never appeared in the game proper, although some are accessible in the game through obscure or not widely-known means:
Several trailers showed footage from a cutscene in Africa of child soldiers being trained to fire assault rifles by an instructor. While the kids training with the instructor can be seen in the final product by going to Masa Village during Mission 13 ("Pitch Black"), waiting until dawn then watching the kids training with the instructor, this doesn't appear as a cutscene.
Another trailer showed footage of a prisoner (dressed similarly to those encountered in Ground Zeroes) being tortured before being shot in the back, in a location that looks very similar to Camp Omega from the same title. While there were claims that this was part of an unrealized Old Save Bonus that would have been accessed through a data transfer and would have involved the player going back to the same location, this cutscene never appears in the game. However, the animations seen in this footage are accessible during Mission 6 ("Where Do The Bees Sleep") — if you follow the soldiers transporting the Hamid prisoner into Smasei Fort all the way down to the basement and not trigger any combat alerts, you can see the soldiers find the Killer Bee and taunt the prisoner before executing him in the same way as the cutscene.
A cutscene of Venom Snake walking through a burned African village, dropping to his knees and screaming up at the sky doesn't appear in the final product, although most believe that these animations were repurposed from Mission 43 ("Shining Lights, Even in Death") where Venom does the exact same thing after he's forced to kill his infected staff members. In the final game, there is a burned village (north of Masa Village) that can be visited and a short cutscene that plays with Miller explaining what happened when you approach a pile of charred bodies, but not the exact sequence seen in the trailer.
Several moments displayed by Venom Snake in Mission 43 are prominent in the trailers, but aren't in the game proper (apparently, most of these were edited by Hideo Kojima to play up certain themes present in the plot, and were never intended to be in the game itself). Among these is a shot of Venom Snake staring away from the flames while cremating his infected troops in Mission 43 (while his face is covered in blood) and a transitional shot of Snake's face turning into a skull (which provides the page image for the game's associated Nightmare Fuel page).
Mortal Kombat X had an announcement trailer of Scorpion and Sub-Zero fighting on the field before Scorpion finishes Sub-Zero.
Sly Cooper: Thieves in Time had tons of scenes not used in the game, including where Carmelita gives dating advice and Dimitri disguises himself as Sly Cooper.
Aliens: Colonial Marines took this to such an extreme that in many countries the trailers were banned or marked with heavy disclaimers. It turned out that almost the entirety of the pre-release trailer was either created purely for the trailer itself, removed from the game for various reasons, or changed beyond recognition by the time the game was released. Things removed included:
One prerelease gameplay reel showed the player using a smart gun from behind a barricade to take out xenomorphs in the Sulaco's cargo bay. Soon after, when the umbilical explodes, the player is shown to have a choice of which way they want to grab onto as objects fly at them into space, implying a Non Standard Game Over for failure. In the final product, no smart gun is ever utilized and the umbilical escape scene is non-playable.
Another gameplay preview showed an entire sequence that never appeared in the game proper. The player character wakes up from a concussion, gives his commanding officer the finger, and they go to secure the operations room in Hadley's Hope. After doing so, the PC and two other AI Marines fend off an attack in the maintenance tunnels with multiple sentry guns, then the PC is knocked out of a window by a xeno, who he subsequently shoots and kills. He is forced to run away from a Crusher charging after him, and barely makes it into the vehicle bay. The group then has a last stand against a horde of xenos (and defend themselves with powerloaders outfitted with flamethrowers) before a Queen busts in, eviscerates several soldiers and attacks the PC.
One trailer showed a shot of the Sulaco and Sephora plowing into the landscape of Hadley's Hope, while in the game only the aftermath is seen.
The original trailer for Amnesia: A Machine for Pigs features a suspenseful scene in which the main character cowers under a stairway as a squealing, unseen monstrosity batters its way into the room. Too bad this event never takes place in the actual game.
The vast majority of the plot seen in trailers and preview footage of BioShock Infinite did not make it into the actual game beyond the broad thematic strokes of the world. This initial gameplay trailer is a good example: though Colombia and the player's fighting mechanics are more or less the same, this entire plotline does not occur in the game and Elizabeth's powers seem distinctly more magical than what she could do in the final game.
The "Holiday Special" trailer for Bully had a unseen scene where the character Gary tells the protagonist Jimmy how "young love... is a beautiful thing", and then pantomimes doggy style sex while saying "spank me". It is probable that this cutscene was removed due to sexual content, which could have hurt Bully's T rating. Not only was the cutscene removed from the game but the dialogue for it was removed from the data files entirely.
Crash of the Titans has four cartoon shorts that show off some of the gameplay mechanics including Carbon Crash.
The trailer for Deus Ex: Human Revolution features several cutscenes that never appear in the actual game. One had Federova gunning down innocent protestors to start a riot, when in the game Federova was dead by the time the riot starts and it appears the police managed to handle the troublemakers without much bloodshed at all.
The announcement trailer for God of War: Ascension had Kratos in blood chains before he throws them and covers the screen.
Due to the infamous amount of Development Hell, most of the game's trailers contain nothing but missing scenes. The game was announced in 2006 as Final Fantasy Versus XIII but wasn't in actual development until 2010 and wasn't released until 2016. As a result, early trailers show very different versions of the games, such as a more violent version featuring humans being killed and unused characters (most glaringly, Stella from many Versus XIII trailers, who ended up replaced with the near identical Luna).
Trailers showed a few segments that were not in the actual game, including a hallway battle, a different design for the king, and a Leviathan battle that appeared more cinematic than the quick time event battle in the released game.
The trailer for Five Nights at Freddy's showed Bonnie the Bunny running down the hallway to the Office. He does not do this in the final game; Foxy takes that role. The clip of Bonnie removing his costume head (revealing his endoskeleton) is not seen in the game, either.
The trailer for Five Nights at Freddy's 2 featured a line from the "Phone Guy" that was never used in the game and only appeared in the trailer. Several shots in the trailer (akin to cutscenes) were only made for the game's promotion.
The scene where Link jumps on a chandelier in the E3 announcement trailer for The Legend of Zelda: The Wind Waker was animated specifically for the trailer. The chandelier exists in the game files but isn't a solid model.
The first trailer had a scene of Link walking through a dark, shadowy forest by the light of his lantern. For some reason there are a lot of cats in the forest as well, implying animals held a bigger role (as do several early screenshots). This forest (dubbed the "beta forest" by fans) was absent from the game. A different unused forest exists as a Debug Room but the actual "beta forest" isn't in the final game.
Another scene from the first trailer showed a small army of monsters marching up a hill and Link riding out to meet them on Epona, set amidst a fiery sunset, and a scene in the second trailer showed Link walking through a forest with some kind of a giant. Both scenes were cut, though it's speculated that the monster army might have been an early version of the Bulbin attack on Karkariko. The giant doesn't appear in the finished game at all.
Phoenix Wright: Ace Attorney Dual Destinies had this gameplay trailer, implying Phoenix himself was the victim of one of the cases. This actually turned out to have been a scene created purely for demonstration purposes that isn't in the final game at all.
Another trailer showed a demonstration of the Mood Matrix mechanic being used to prove that Ted Tonate is the first case's culprit, with a completely different motivation than the one he haves in the actual game.
A trailer for South Park: The Stick of Truth includes a giant Clyde Donovan busting through city hall, and the Vampire Kids. The Vamps only appear in a cutscene in Clyde's fortress then are never seen again. On another note, Crab People and Hippies were seen to be fightable enemies but only one Crab Person appeared in the game as a friend. Justified since the script was 850 pages long and they had to trim it down.
The reveal trailer for Splatoon 2: Octo Expansion shows Agent 8 spotting Inkopolis Square in the distance after emerging from a subway tunnel. This scene never appears in the actual game; Agent 8 instead emerges from an underground testing facility and is picked up by Marina and Pearl via helicopter.
The promotional trailers for The World Ends with You contain more than a few scenes that never made it into the game, like Neku flying up the side of a building and an extra scene by the Udagawa tag wall. Many fans mistakenly believe that those scenes were specifically cut from the English-language version, mostly because they are among the most popular scenes to include in fanvids.
Undertale parodies this in the release trailer. In-between shots of in-game footage, suddenly, inexplicably, a weird blobby 3D model of Toriel rams itself into a pile of untextured cubes and flies away as a ghostly, photo-realistic version of the same character says "my child you are breaking my heart". (The game itself is entirely 2D.) A caption underneath notes that this is "PROBABLY NOT ACTUAL GAME FOOTAGE?" Its PlayStation 4 trailer showed the same scene, now captioned "PROBABLY STILL NOT ACTUAL GAME FOOTAGE?", and the Nintendo Switch trailer takes it even further. This time, instead of crashing through blocks, she's flying after Mew Mew, firing lasers from her eyes that cause explosions, while the realistic Toriel in the background now says "My child, I shall break your heart." There's also some random trees and blocks in the background, one tree of which has Flowey's face, as well as a monster truck driving past. And the note now says "TOBY WHERE IS THIS FOOTAGE EVEN COMING FROM??"