Ah! My Goddess maintains the status quo for 20 years. Keiichi and Belldandy are the exemplars of the Chastity Couple. And then in chapter 285, Hild explains that Keiichi's mind has been altered by the forces of heaven to prevent the relationship from developing further. Apparently, the goddesses knew all along. It may take readers a while to sort this all out.
Even more so episode 9, which reveals the causes of the jumps.
Angelic Layer contains a giant one in episode 24, though it's for a character rather than the viewers. At the end of the episode, the champion of Angelic Layer reveals that she is Shuuko, Miskai's mother, who Misaki hasn't seen in years. Episode 25 then shows the impact of it resulting in a brilliant tearjerker episode in an otherwise light hearted show.
All hell breaks lose in episode eleven when the rest of the class hears the tape from years ago which says the only way to stop the calamity is to kill the ghost student. In their fear-stricken panic, they all decide that Misaki Mei is the extra student and go batshit insane, chasing her around the creepy hotel trying to murder her. They accidentally kill their own teacher, who tries to protect Mei, and two of the students end up dead during the chase. There are at least three other murders/deaths outside of that incident in this episode as well.
Chapter 130: Someone re-enacts a prank that was discussed in Perfect Crime Party, and it gets on the news. Since the manga had a fair share of parents criticizing it for fear kids might imitate it, this does not bode well for it.
A few chapters later, it's revealed that the manga Niizuma wants to end is Crow.
Chapter 3, which features Yoshitoki's death an shows that Anyone Can Die
Chapter 10, which features the deaths of Izumi, Ryuhei, Hiroshi, and Mitsuru, the most of any chapter, and the revelation that Kazuo is playing.
The Eclipse (Volumes 12-13) arc of Berserk would have been the greatest wham ever, with the HSQ through the roof stratosphere, had not the end of the Guardians of Desire arc (Volumes 2-3) just before the big Golden Age arc hinted at essentially given away what would happen. It was, regardless, a very powerful Gut Punch.
More properly played straight in the anime, which cut out the Guardians of Desire arc altogether. Although the events of the Eclipse were strongly foreshadowed, the last few episodes still constitute a pretty powerful Wham.
In Chapter 307, Femto uses the power of the Skull Knight's Sword of Resonance to tear open the bonds of reality, and merges fantasy and reality.
Black Butler has quite a few of these, but probably the biggest example is the episode where Ciel goes back to England to find that it's on fire.
Episode 6 of Blood-C. Episodes 1 through 5 followed the same formula, sing on the way to school, play with the puppy, eat with friends, fight and kill the Monster of the Week. 6 takes the formula and shatters it, with the deaths of Saya's friends Nono and Nene and several townspeople in a rather shocking bit of Daylight Horror.
And if you thought 6 was bad, 8 and 9 go straight past it with a monster attacking the school and killing EVERYONE in Saya's class, even her friend Yuka. The only survivors are Saya, Tokizane, and Itsuki
Add yet ANOTHERWham Episode with episode 11. To wit, The Motoe Twins, Tokizane, Yuka, Itsuki, Fumito, and Kanako are all actors, and Saya's whole life in town was part of some twisted Truman Show Plot.
Bokurano: Every time a detail is revealed about the battles that take place in Bokurano can qualify as part of a Wham Episode. In particular, one occurring in both the second episode and chapter where it turns out whoever is chosen to be the main pilot for a battle dies as soon as the fight is over and still later when it is revealed that when a battle is over, whoever loses has their entire universe destroyed. Those two points end up setting the tone and sense of desperation for both versions of the series.
Chrono Crusade, ep 19. The Big Bad has been subverted so far, everyone's enjoying a carnival...and Mr. Big Bad himself comes out of nowhere, assembles all his MacGuffins in one slick move, and accomplishes the very thing the heroes have been trying to prevent him from doing!
This actually is based on a plot twist that happens in the manga—only the manga version has even more wham, since it also includes Chrono finally breaking down and snapping after years of mental anguish, flying into an Unstoppable Rage that destroys part of San Francisco and ends with him having a Heroic BSOD that lasts for more than an entire volume!
CLANNAD ~After Story~ episode 16. Even though the drama of the recent few episodes had revolved around the possibility, nothing can prepare you for the sheer impact of Nagisa's death in childbirth.
And the same goes for ~After Story~ episode 22, where Tomoya initiates a Time Skip thanks to the death of the girl from the illusionary world, who is actually Ushio after she loses her memories when she died, by obtaining a light orb, and using said light orb, travels back in time and is given a second chance to witness Nagisa's childbirth. This time around, she lives.
The Recap Episode of all things, can be considered a Wham Episode because it's confirmed that the reality where Nagisa, Ushio, and Tomoya died really happened.
Claymore: Any chapter where Miria shows up is bound to be a whammer in some way or another. One of the most shocking so far is scene 79, when she reveals to the Seven Ghosts, Galatea, Clarice and Miata that the Organization has been the body responsible for creating the yoma, which they fight. According to her research, the mainland, which remains ambiguous to just about the entire population of the island, is in chaos due to an ongoing war. One side, the side in which the Organization originated from, decided to experiment with making elite super soldiers in order to combat the super soldiers of the opposing side (the Dragon Kin). In short (and put in Miria's words): the entire island is the Organization's laboratory. And those super soldiers in question? They're the Awakened Beings.
Episode 22 of Code Geass is pretty much the nuclear bomb of wham episodes; a thirty second scene causes the entire show to do a 90-degree turn on its plot axis, and depending on what camp you fall into, at this point the show either poorly attempted to recreate the death of Lalah Sune and forced it or filled in nicely.
The last five episodes of Season 2 were basically the collective wham of the entire series, with everyone's roles turned upside-down: Lelouch, former leader of The Black Knights, becomes the Emperor of his enemy Britannia; his former enemy Suzaku becomes his bodyguard; Kallen, who spent most of the show with a Bodyguard Crush on Lelouch, chooses heer beliefs over him and will stop at nothing to kill him; and Schneizel, Prince of Britannia, joins forces with the very organization Lelouch created. Also, after Lelouch's primary motivations for the first 90% of the show involved avenging his mother's death and creating a gentler world for his blind, wheelchair-bound sister, Lelouch discovers his Lady Macbeth mother's still alive and promptly becomes a Self-Made Orphan, then creates a brutally oppressive regime bent on world domination, and when his beloved little sister begs him to stop, he makes it clear that he won't hesitate to kill her if it's convenient to his plans. And the clincher? It's all an act to unite the world with his death. It worked out somehow.
Well, in Kallen's defense, the only reason she chose to stand against Lelouch was because she believed he didn't care about her, not so much because she believed he was wrong. This is pretty much confirmed in her character poem, which states that had Lelouch spoken up at the time their kiss, she would have "followed him to Hell"; naturally, Lelouch knew that and so kept silent so that she would live.
Chapter 16: Nunnally breaks her contract with Nemo and gets captured.
Chapter 20: The Emperor has a coup to replace the established governments of the Areas with his own men, and moves to put his Assimilation Plot into action.
Episode 6 of The Daughter of Twenty Faces comes out of nowhere and sends earthquakes through the viewer's previous suppositions about the show and its content.
Chapter 55 of Deadman Wonderland. Up until this point, it's establshed that Shiro has a Superpowered Evil Side known as the 'Wretched Egg.' And then clear out of nowhere, it turns out she never had a Split Personality at all; she faked the whole thing. Why? Because underneath it all, the sweet, bubbly, adorable Forgotten Childhood Friend of Ganta's he knew and loved was actually a violent, hateful yandere who had never forgiven Ganta for abandoning her when he she needed him the most, and used the Split Personality act as an excuse to both be with Ganta as she was in her childhood, and exact revenge on everyone who had ever hurt her while making Ganta suffer in the same way she had by taking everything he loved from his past life away from him. And it gets worse: She did this because she wanted Ganta to eventually get strong enough to put herout of her misery.Damn.
Episode 21 of Dennou Coil. Turns out Isako's brother was dead all along (she thought he was in a coma before) and she was strung along by Nekome.
Episode 4 of Diebuster: Up till this point, Nono has been basically a tag along to the Topless, hoping that she could gain her own Buster machine to defend Earth from the Alien Monsters. When archaeologists on Titan discover what they believe to be an ancient, incredibly powerful Buster machine, Nono violates orders to get close to it. As punishment, the Serpentine Twins, Leaders of the Topless, send her on a Snipe Hunt to Pluto to retrieve what may possibly be an intact Buster Machine, that crashed there some years previously. When the Titan excavation completes, three things are revealed simultaneously: The Alien Monsters they've been fighting up till this point aren't Alien Monsters at all, but part of a forgotten defense system designed to destroy threats to Earth; The "Buster Machine" on Titan isn't a Buster Machine at all, but one of the real Alien Monsters from Gun Buster; and that Nono is actually Buster Machine No. 7, the control unit for the Defense System and one of the most powerful Buster Machines in existence.
Digimon Tamers goes from fantasy-violence kiddy hero show to mind-rape extravaganza when Beelzemon kills Leomon, later following up with possibly the most destructive and disturbing Big Bad in Digimon history, the D-Reaper, possessing Juri's voice, memory, and for a while, her very appearance.
In Digimon Adventure, we have Wizardmon's heroic sacrifice and subsequent death at the hands of Myotismon. For many, this was the moment when the show started Growing the Beard and showed a greater amount of depth than ever before.
Digimon Savers follows suit with the death of Merukimon and the reveal of Kurata's true intentions, as well as the past these characters share. It cements Kurata as irredeemable and from then on he just keeps getting worse.
When Goku tells Bulma, Yamcha, Oolong and Puar about the night a giant ape monster killed his grandpa when the moon was full. After a few minutes of Goku's reminiscing (in which he recalls how his grandpa told him never to look at the full moon) the gang, petrified, scoot into the corner and deduce that Goku was the monster that night.
Yamcha: I-I-I had a f-feeling he wasn't an ordinary k-k-kid...!
Bonus points for Oolong's question after their escape: "So what is he, some kinda space alien?" Fast forward to the beginning of Dragon Ball Z, where we find out that this is indeed the case.
Krillin's first death. After a tournament, the gang go out to eat, but Goku realises he's forgotten something, so Krillin decides to go back and retrieve it. Goku has an uneasy feeling throughout dinner and finally snaps and runs back to the tournament grounds... to find Krillin dead. This set the tone for the King Piccolo arc, and is considered to be the turning point of the show when it became more serious.
The first time Goku transformed into a Super Saiyan, a direct result of Freeza killing Goku's best friend, Krillin (yes, again) and mocking him after the fact. Before that, Piccolo's seemingly senseless sacrifice, thankfully Freeza didn't mock Piccolo. Not just because the whole scene was epic but also because the normally cheerful Goku's disposition drastically changed. Besides the fact that he was revealed to be the legendary Super Saiyan, his looks changed and he became more powerful. No one was quite sure of what was going on with him; not his son Gohan nor Freeza nor the audience.
A minor one in the beginning of the Android Saga, when it was revealed that the mysterious sword wielding Super Saiyan was in fact Trunks the son of Vegeta and Bulma... who hasn't even been concieved yet.
Trunks' entire introduction prior to this was a Wham moment too. Prior to this, the it was firmly established that the only living Saiyan characters were Goku, Vegeta, and Gohan. His reveal as a Super Saiyan revealed that somehow, someway, there was somebody else with Saiyan blood.
When Goku had to distract Majin Buu the first time he fought him everyone thought he would share the same fate as Majin Vegeta . That was until Goku revealed that he had a Super Saiyan 3 transformation. This of course shocked both the audience and the characters a bit, echoing the Super Saiyan transformation in the Freeza Saga. This ended up as a Crowning Moment of Awesome in the show showing one of the most spectacular transformation sequences ever.
Durarara!! has Episode 11. The leader and the founder of the Dollars is revealed.
I'd argue that it's actually Episode 10. Even though the fact that Mikado is the leader of the Dollars isn't explicitly stated until Episode 11, the end of Episode 10 strongly implies it. The Wham comes from the realization that this supposedly nice, innocent kid is actually a badass with a better handle on the situation than anyone else and that the seemingly inane details that fill the rest of the episode are not only important, but do a masterful job of setting up the end reveal. This was the episode that made the show go from "quite good" to "absolutely incredible."
The person behind the Slasher attacks in episode 'Mutual love'.
Episode 25 of Fancy Lala where not only the titular character loses the item to transform, but also loses Mogu and Pigu.
In the very first one of Fullmetal Alchemist, the Generals of Central reveal to Mustang that they knew King Bradley was a Homunculus. They then disband Mustang's group forcing Fuery, Breda, and Falman to the borders of Amestris, and Riza Hawkeye becomes King Bradley's secretary, so that she can be used as a hostage.
Pales in comparison to the meeting between the Elrics and Father. In the course of a chapter its revealed that Father is not Hohenheim (but he knows him), he can prevent anyone from using Amestris alchemy, but Xing Alchemy can function. Scar finds out that the Homunculi started the Ishval War, and Ling is possessed by Greed. The next chapter reveals that Greed has no memories of his past life, and Ling is still in there.
Gluttony almost kills Riza, the Mustang crew learns about Homunculi, Havoc's spinal cord is severed, Roy gets stabbed in the ribs, Al almost dies, Riza learns Mustang "died" and starts screaming, crying, and has a Heroic BSOD, Mustang comes back and we learn that Homunculi actually can be killed. All in one episode.
And Ed finding Al's body behind the Gate? Gosh dang.
We also find out later that Hohenheim IS basically the Philosopher's Stone, as well as possibly the founder of modern Alchemy. Small wonder his kids are prodigies.
And of course there's always the episode in Brotherhood where Ed is impaled through his abdomen by a metal rod when Kimblee blows up the room. Meanwhile, Al feels his soul being ripped from his body.
Then in Chapter 104, Father reveals that his plan is to open the Gate of Truth for the planet. He also activates the country-wide transmutation circle, sucking out the souls of almost everyone in the country. Then he absorbs GOD into his body.
In chapter 107, Al reverses the transmutation Ed did to attach his soul into the armor, returning Ed's right arm and getting trapped into the Doors of Truth in process.
And let's not forget the 2003 anime adaptation, such as when Hughes died, or when it turned out that the Homonculi were behind the Ishvalan war, or the second to last episode. What, the other side of the gate is our real world? And you mean to tell me that alchemy is powered by the deaths of people in this world? (Meaning that part of the reason that all these plots are happening now is that Alchemy in general is being supercharged by deaths in World War II and the Holocaust!) WHAT, Envy is really Hohenheim and Dante's son? HOLY CRAP did Ed just die?!
Don't forget the reveal of Dante and Hohenheim's secret in Episode 45.
A Certain Scientific Railgun is a lighthearted show, till all of a sudden Harumi of all people turns out to be a villain. That's surprising, but that's not the real wham. The real wham is when some sort of bizarre creepy fetus thing comes out of her and lets out a inhuman roar.WTF moment for sure.
Gaiking Legend of Daiku Maryu episode 28... wherein Smug Snake and Magnificent Bitch Proist singlehandedly delivers sucker punch after sucker punch to the protagonists, seemingly convinces a young girl to kill her own father, and just continues to make a living hell for everyone. With the exception of the whole "Limitation Syndrome" episodes, all those other light-hearted episodes seemed a lot more appropriate and necessary, with Proist rapidly become just as hated as Fucking Ribbons.
The first three episodes of Ga-Rei -Zero- are Wham Episode. First, the supposedly-main-characters are killed in episode 1. Then, the bloody murderer in the episode before is introduced as a lost member of another squad. And then, in the third episode flashback begun, which has nothing similar with the high body count of the first two episodes.
The final "attack" of the Individual Eleven in the second season of Ghost in the Shell: Stand Alone Complex. Twelve terrorists join together to commit their greatest and final "attack", all of them bringing katanas with them. A police team is racing against time to stop them, when a news-helicopter spots them first on a skyscraper roof, broadcasting everything on live-TV. And without any warning they pull out their swords and decapitate each other!
Giant Robo: The Day The Earth Stood Still episode 3, at very end. Daisaku and Giant Robo finally arrives at the battlefield, Daisaku gives a speech about how he can never forgive all the evil Professor Vogler did and orders Robo to attack Volger Sphere. But when Robo puches it....his arm breaks into the pieces. Also, next episode, in which several characters are Killed Off for Real.
Great Teacher Onizuka had a veritable WHAM clusterfuck when Urumi posted a website showing video of Miyabi doing personal stuff around her house (she discovers hidden cameras in her bathroom and bedroom). Onizuka races to find Urumi before she kills herself while his students must find a way to shut the website down. Teshigawara convinces the vice-principal to kill Onizuka but all that was a smoke screen so Teshigawara can kidnap Azusa.
Guilty Crown has so many of these that it's easier to count the episodes that don't qualify. Every single episode after episode 12 certainly does qualify. Up until that point, it seemed like just another overall awesome action-anime, but after Shu kills Gai in episode 12, it becomes a whole lot Darker and Edgier. To the point where it actually starts having Wham Half-Episodes. The list on the page for Guilty Crown is simply so long that the show seems to want an entry on Serial Escalation! It now has it's own page.
Episodes 12 and 13 of GUN×SWORD, wherein Van catches up to the Claw, learns an unpleasant fact about Dann, and is forced to kill a close friend. Also revealed: Michael, Wendy's brother, now serves the Claw.
Guyver: There are a few, especially as it's a constantly-escalating plot, but the most infamous is when Sho's father becomes an unwitting Enzyme-type Zoanoid who rips the Guyver's brain out, forcing the Guyver to kill him on autopilot.
The appearance of Archanfel, the Big Bad of the series, and the leader of the Zoalords. He gets sucked into a black hole, climbs out a couple of chapters later, and turns Guyver I and Guyver III's Mega Smashers back on them, nearly killing them in the process. As this takes the Guyver units out of the picture for a large chunk of time, the Zoanoids use the lack of any real threat to their powers to Take Over the World.
Hanaukyō Maid Tai La Verite episode 7 "Unidentified Living Creature". Up to this point in the series the episodes had been light-hearted and comedic. An earthquake reveals a tunnel leading under the mansion. Deep underground the mansions there's a smaller duplicate mansion. Inside the duplicate mansion Chief Security maid Konoe Tsurugi finds on old portrait of a woman who looks exactly like Head Maid Mariel. This leads to a chain of events that result in Mariel falling deathly ill, being kidnapped by Taro's grandfather's minions and having to be rescued, all as part of the grandfather's plans.
HeartCatch Pretty Cure!begins with a Whame Episode two-parter. Cure Moonlight's defeat, Cure Blossom's introduction leading into a Cliffhanger... which is started off with her going into a mass panic. This was not going to be a regular Pretty Cure series.
Then you got Episode 10, which really puts the breaks on the fun when the Dark Precure shows up, hands Blossom and Marine their asses, then disappears.
Heroman episode 4 was one, being the first time Joey and the eponymous robot couldn't do anything but stall, and one of those things was hard to stop, but at the end of the episode, more pop out, episode 5 established that the Skrugg aren't so Genre Blind, and they promptly try to remove the threat with new, human soldiers (who turn out to be the Jerk Jock and his little buddy).
Episode 13, Joey comes home from a date, his friends tell him that the government is after him, and he may have to leave, he does.
Higurashi itself has a few. For example, episode 25 where you learn that the entire first arc was from an Unreliable Narrator's stand-point and he was hallucinating. The second season has numerous once we learn the plot, also one episode ends with everyone dying, right after it looked promising that they would be safe.
Episode 10 of Hyperdimension Neptunia; while the rest of the show mixed things up a little, it essentially followed the plots of the second and third game. However in this episode when Peashy is freed from Anonydeath's control instead of it and the following moments being a Crowning Moment of Heartwarming like in the game...you get a tearjerker of incredible proportions since Peashy doesn't remember anything, unlike in H.N. Victory where she ends up glomping Neptune. The stark change to drama in what has almost always been a Comedy Anime, is a pretty big moment by itself; but the Tearjerker aspect when compared to the source material makes it have even more of an impact.
Episode 42 of Kamikaze Kaitou Jeanne has three revelations. The titular character is an Unwitting Pawn all this entire time, her helper Finn is turned evil all this entire time, and Miyako has finally gets the chance to discover the titular character is none other than her best friend, Maron Kusakabe. Ouch.
Chapter 12 of Karakuridouji Ultimo. After introducing a whole bunch of new doji, in the previous chapter, new Evil Doji are introduced, who proceed to murder the Good Doji in brutal and disturbing ways, kill all the good doji members in almost as brutal ways. Then the world blows up killing anyone who had any ounce of life left. Yamato and Ultimo manage to use Time Manipulation to save everyone at the last second, but, the fandom still probably suffers from that chapter.
Chapter 21 in a different sense. Anybody who was uneasy about Yandere, stalker, and Depraved Homosexual Rune, proabably had a nervous breakdown when that chapter rolled around. Turns out Rune has no problem resorting to rape to get Yamato. It was only attempted in the end, but still, it's not something that most people wanted in their head.
Chapter 466 of Kenichi: The Mightiest Disciple: Kenichi and Miu, in escaping from Silcardo Junazard's base, are confronted by several master-class martial artists. It looks hopeless, as they're both worn down and out of energy...then suddenly John the mercenary, previously established as a buffoon, shows up to rescue them, fending off the would-be killers! But that's not the Wham moment...it's when, after a section of the burning room falls on John, his skin and clothes burn off—to reveal the tall, lean, muscular, serious form of SaigaFurinji, a.k.a. the "One Shadow" of Yami, a.k.a. the series' Big Bad.
Episode 15 of Kiddy Grade ends with the destruction of GOTT headquarters, with the following episode introducing Eclair as acting chief of the "new and improved" GOTT... or so one would think.
Episode 20 of Kurau Phantom Memory offers a major change in the premise of the series by introducing Rynax with evil plans to take over the world, who want to use Kurau for their purposes.
Legend of Galactic Heroes is very liberally sprinkled with this indeed, throughout its long run. This is to the point that every few episodes a Wham would happen. Here are some examples (the following list is NOT exhaustive):
There are two well-remembered Whams. The first is Episode 26: Farewell, the Old Days. The cliffhanger on Reinhard's assassination attempt is resolved most unexpectedly: His best friend and right-hand man, Siegfried Kircheis, dies protecting him. It's a significant Wham since, up to this point, Kircheis was one of the main characters.
The second one is, of course Episode 82: The Magician Doesn't Return, a title which clearly spoils Yang Wen-Li's demise. Everything in the episode seems to be pointing towards a daring, last-minute rescue. That is, until the last minute, when the narrator makes it very clear that Yang has just bled to death. This is, again, unexpected and changes the entire dynamic of the show, since Yang was the driving force of one of the two main Cast Herds.
There are many other Whams that are hugely significant to the show's various arcs. The Kaiser's death to illness in season 1 robs Reinhard of one of his motivations and sparks a civil war in the Empire, which causes Reinhard to engineer a civil war in the Alliance, contributing to weakening the Alliance and enshrining his own position. In season 2, he then uses this to wage a campaign against the Alliance, occupying previously-neutral Phezzan, and closing the season with the unification of the galaxy under his rule, plus an Awesome Moment of Crowning, which cements his authority over the Empire. The Legend finishes, but the list goes on...
In Chapter 16 of Letter Bee, Lag encounters his old friend Gauche, and learns that he lost all his memories, joined an anti-government organization as a "marauder," and has a mysterious girl with him who has the same name as the dog that used to be his dingo.
Episode 21: Ends on a character wham, Ranka runs away from Frontier with Brera.
Episode 24: Ranka singing for the enemy and Alto getting shot down in a ball of fire. Given the condition at the end of the episode, it really was looking like a Kill Them All, as practically the only good guy left is the terminally Ill Girl.
In A's Episode 9, the protagonists accidentally encounter the Wolkenritter while visiting Hayate, and prepare to fight them. But then it turns out that the mysterious man who's been helping them is actually two people, and they absorb the Wolkenritter into the book and trick Hayate into thinking that Nanoha and Fate did it, causing the Book to awaken, possess Hayate and set out to kill the heroes.
In episodes 16 and 17 of StrikerS, Jail Scaglietti's forces attack Riot Force 6's base and the site of the press conference, abducting Ginga and Vivio (after almost killing the first) and showing the power of the Combat Cyborgs. During this attack, it is revealed that the Nakajima sisters are also combat cyborgs.
Magical Project S is a hilarious parody of the magical girl genre and never takes it self too seriously. Until episode 19 where it's revealed to Sammy that her best friend, Misao, was Pixy Misa, the evil magical girl that tortured the main cast (Sammy included) with her magical powers, and she was about to harm her parents. Also, that Misao was in fact an Stepford Smiler and Beneath the Mask feels lonely, worthless and jealous of Sammy's happiness. Rather than the brainwashing the audience had been led to expect her evil alter ego was in fact really her all along (albeit her repressed feelings).The only thing Rumiya did was "unleashing" her Hidden Self. Nice job, Ramia.
The first "wham" comes at the end of episode 8 of the Mai-HiME anime, when Akane goes into an Heroic BSOD and has to be put into hiding after watching her boyfriend Kazuya die when Miyu destroys her CHILD, showing her (and the viewers) the true cost of protecting the ones you love. This one was immediately followed by a breatherBeach Episode, which still managed to sneak in a little plot and Character Development unexpectedly.
However, an even bigger "wham" hits at the end of Episode 16. The heroines have defeated the invading Searrs army, and decide to celebrate with a night of merriment and karaoke. Once done, they're all ready to go out and kick some more Orphan butt...except Nagi, who has isolated them from Mashiro and Fumi (who helped them fend off Searrs), tells them that the Orphans aren't coming anymore, and forces them to fight against each other to ensure the world's survival.
Episode 16 of Mai-Otome: The reconstruction of the portion of Mashiro's castle that was destroyed in an earlier episode is finally completed to coincide with Garderobe's graduation/advancement ceremony, and the large curtain is removed to reveal...a Schwarz superweapon capable of summoning Slaves en masse to every corner of the planet.
Then, in Episode 17, Schwarz invades Garderobe and holds the entire school prisoner, with Shizuru offering herself as a hostage to allow Natsuki time to escape and seek help. Meanwhile, on the other side of campus, Nina has contracted herself to Nagi (the mastermind behind the whole takeover), who flips out and attacks Arika out of jealousy when she learns that her adoptive father Sergey was Arika's Mysterious Benefactor, thus enabling her to attend Garderobe in the first place. And then, their friend Erstin is revealed to be a Schwarz sleeper agent, and is Killed Off for Real trying to stop the two of them from fighting.
Mai-HiME manga: The chapter after Nagi's defeat and the subsequent victory parade. In comes the Searrs Institute for Girls (led by Natsuki's mother, whom she believed to have been killed) to enact a hostile takeover of Fuuka Academy.
Also, episode 13: the heroes capture an enemy mech and it has a cockpit full of Gekiganger 3 merchandise, thus proving that the "alien invaders" are actually humans.
This extends into episode 16, where the history of the "alien invaders" is revealed.
Mazinger Z: The final episode was an endless succession of shocking moments altered the status quo irremissibly: it was revealed that Gorgon was actually working for someone was infinitely more powerful and most dangerous than Dr. Hell, Mazinger-Z was utterly and easily defeated by a new enemy, a new and more powerful Mazinger showed up, named Great Mazinger and it was revealed Kouji's father was alive. The Wham factor was even bigger in the movie version of that episode, when the Mykene army razed to ruins New York, London, Paris and Moscow in one single stroke before leading towards Tokyo and destroying it as well, and at the end of the movie, the prophet removed his mask and revealed his real identity: Kenzo Kabuto, Kouji's father.
Long before there was an episode where the villains took over a Japanese village in a very Nazi-like manner, including a systematic slaughter of the civilians that they considered "useless" and usage of the women of the village as human shields for their latest Mechanical Beast. That was quite shocking and brutal, too.
Episode 40 of The Original Series ends with the Zeon firing the Solar Ray Kill Sat that destroys a third of the Federation fleet and kills both Zeon leader Degwin Zabi, and Federation Fleet commander General Revil. The real Wham? Earlier in the episode Amuro attacks Char, but Lalah Sune, the woman both men loved, intercepts the attack and dies. The result is that Char now hates Amuro for killing Lalah, while Amuro hates Char for letting Lalah fight. The rivalry ends in Char's Counterattack when both die during the battle.
Like anyone didn't see that coming, especially after the previous fates of Icelina, Hamon (Ranba Ral's girlfriend) and Miharu (the Zeon spy that Kai fell for). Doesn't help that Lalah was introduced only a few episodes back, yet held such a big impact on both Amuro and Char in her first appearance; that's practically a bright flashing neon sign that reads "DEAD GIRL WALKING!"
Zeta Gundam is more of a string of wham episodes than anything else. Most notable are episode 3 where Kamille's impulsiveness causes the death of his mother Hilda while trying to save her. Then of course, we have the death of his star crossed girlfriend Four in episode 36 (again, at least partially caused by his recklessness) and episode 50 with one of the bleakest endings in all of anime.
Gundam ZZ has several, including the episodes dealing with the Colony Drop on Dublin are especially jarring when longtime Gundam survivor Hayato dies a classic, Tomino-esque pointless death. This means that Karaba's down the drain and the Argama and company are literally the last line of defense against Neo Zeon. The aftermath, including Puru's death, are no less shocking and this "unserious" installment in the franchise doesn't give us a Breather Episode until we get back in space.
G Gundam has episode 14, which reveals that Domon's teacher, mentor and father figure Master Asia is working for the Devil Gundam and brainwashed 4 other pilots. It also introduces the rest of the Shuffle Alliance 4 pilots who are supposed to work together with Domon to protect the Earth. Episode 42 reveals that Doctor Mikamura, Rain's father, betrayed his best friend Domon's father by revealing to the Neo-Japanese government the Ultimate Gundam. It also reveals that the supposed Big Bad is good, and is a brainwashed victim of the actual Big Bad. Also, episode 40 is where we find out that Domon's mysterious Big Brother Mentor is a clone of said implied Big Bad. There's also the fact that Master Asia is, unlike the Devil Gundam's other minions, Not Brainwashed. He joined its mission to rid the Earth of humanity of his own free will.
Gundam 00 basically pulled Wham Episodes rapid-fire since the Throne Gundams came out of the sky and Nena blowing up a certain wedding in Spain, totally wrecking the lives of Saji and Louise. Let's just say that fans spent at least two months screaming at their screens when yet another cliffhanger got thrown out there.
And to not be less than the other series Gundam AGE has episode 14. Yurin L'Ciel, massive Ensemble Darkhorse and the most likely candidate to become Flit's girlfriend, is horribly killed off (as a homage to the original example above), which ultimately makes the traumatised Flit switch from Messianic Archetype to Dark Messiah.
In Muhyo And Roji, the competition between Muhyo and Goryo concludes with Goryo winning on a technicality, resulting in him winning control of Muhyo's office. Muhyo effectively puts Roji on leave, and tells him that he's fired if he doesn't learn what he has to do by the time they meet up again.
In Murasakiiro No Qualia, Chapter 6 finally reveals the pecularities brought along with Yukari's eyes. And... they're creepy, at the very least.
"This is the point of no return. You have been warned."
Mythical Detective Loki Ragnarok, Episode 21. Heimdall's death scene. Long story short: He trapped the main character and friends in an alternate dimension, eventually dragging the MC into a creepy platform strikingly reminiscent of the Great Bridge of Hylia. He then goes completely unhinged, exhausting very literally every ounce of his considerable power (which he had just gotten back from a certain thief) on the character he believed to be that thief — the main character. Said character then deflects one of Heimdall's attacks and uses it to kill his only friend in the entire series, a falcon, leaving an unholy mess of feathers to rain down upon Heimdall. He goes totally off the deep end and winds up shattering at least 90% of the platform they had been previously standing on without even moving a muscle — it just cracks under their feet. He then falls to his death with a truly cringe-inducing scream... and the normally stoic main character, after being returned to the real world, sheds a single tear. Keep in mind that this is coming from the same series which, a few episodes previous, was doing an Iron Chef parody.
The first few episodes of Nadia: The Secret of Blue Water were pretty lighthearted. The two main characters were mostly running around, some Team Rocket-like jewel thieves were chasing them, and the titular Nadia was trying to find a way to get to Africa. Then they end up on Gargoyle's island and boy, things get REALLY dark out of nowhere. Most of the people on the island have been killed by Gargoyle's men. The main characters find a little girl whose parents and even dog were just killed, and it's a life or death situation when they all have to hide from them. It's truly scary.
Needless begins as a ridiculous and humorous series...up until Episode 16, in which Cruz is fatally injured and killed, as opposed to previous episodes in which his injuries were always played for laughs.
Episode 18: The dummy plug system is activated, and the pilot of Unit-03, who is revealed to be Touji, is mortally injured (he dies in the manga).
Episode 19: Unit-01 shows undeniable proof that it's alive.
Episode 21 is the point where the show gets Darker and Edgier by killing off Kaji just after the The Reveal that NERV is holding Lillith, not Adam, inside Terminal Dogma.
Episode 22: In one of the most traumatic and terrifying moments of the franchise, Asuka is Mind Raped into a coma, while revealing a backstory that is even darker and more traumatic than Shinji's or Rei's.
Episode 24: The replacement for Unit-02 arrives, and befriends Shinji instantly. Too bad he's the final angel. After running away, again, NERV agents finally find Asuka, alive, in a bathtub full of blood after a suicide attempt by slitting her wrists.
More like Episode 13. After the big bad is defeated, Stocking casually wonders if angel weapons work on angels. She then proceeds to kill Panty by slicing her into 666 pieces, in order to resurrect the Big Bad, say "I'm actually a demon", and then walks off into the distance with the aforementioned big bad.
Despite being based on an earlier work, Pluto has a few:
In a flashback Gesicht hounds a human being into a corner and murders him, overcoming his in-built robotic rules through sheer hatred.
Gesicht, the main character, is murdered three-quarters of the way through.
Brau 1589, the resident psychopath and Hannibal Lecter expy, spares the Thracian president and sacrifices himself to kill the real mastermind on the very last page.
The Best Wishes! saga of Pokémon usually upsets the status quo. But the 18th episode has Ash capturing Sewaddle, breaking the format of Ash capturing only 6 Pokemon per Region. Ash, so far, has caught nine Unova Pokémon.
Fans of Pokémon Special were floored in the BW arc, when White's star Pokémon actress, Gigi the Tepig, willingly ditches her to go off with N. The shock was enough for White to accidentally slip out of the Nimbasa Ferris Wheel, leaving her to fall hard on the ground, barely conscious and her blank eyes full of tears. Considering how the rest of the franchise seem to have Pokemon unconditionally love their trainers no matter what, it was an especially big shocker.
Queen Millennia: A dozen or so episodes in it is revealed that the leader of the terrorist group attacking the main characters is in fact Yayoi's sister, the original choice for the Millennial Queen, and that she did a Face-Heel Turn to the humans' side. Which Yayoi is NOT on. Yayoi then does a Face-Heel Turn of her own against her mother and sides with the thieves. This changes how ALL the factions in the series were seen until then.
RideBack: Though the show is clear that it's a dark take on things, Rin's friend, Suzuri, is the one keeping the show as light as it is. She's showing off having fun when the government decides that Rin is to be considered a terrorist and needs to be stopped. They decide that the one showing off is the terrorist. It doesn't help that the preview for the next episode focuses on Suzuri acting like herself.
Rosario To Vampire has had several, among them include Tsukune gaining powers from vampire blood, Tsukune being turned into a Ghoul by said blood, and most recently, Outer Moka dying
The Sailor Moon anime has various Wham Episodes; for instance, Chibi-Usa's new friend, the Ill Girl with the healing powers? After a couple of episodes, it turns out her dad is the season's Big Bad.
Also, in the previous season, when Chibi-Usa is revealed to be Sailor Moon and Tuxedo Kamen's daughter, and by association, later, that Sailor Moon and Tuxedo Kamen are going to be King and Queen of Crystal Tokyo.
The first Wham Episode in the series is probably the one where Nephrite dies. Before that, it was mostly about the wacky adventures of three clumsy superheroes and their talking cat; this episode marks the first time someone other than a Monster of the Week actually dies (as opposed to being frozen in a crystal), leaving another character heartbroken, and things generally take a darker turn from here.
School Rumble had Eri then Yakumo introduced as potential love interests for Harima. The manga showed Karasuma admitting he really is in love with Tenma and he has a terminal disease.
Sekai de Ichiban Tsuyoku Naritai: Blue Panther, thought to be, for 2 episodes, Misaki's rival Juri, was in fact revealed to be a rival, yes...but Sakura's rival, Elena.
To sum up the episode, Chiaki thinks that Hatori is cheating on him with his ex-girlfriend in high school and that he deliberately skipped out on their date to see a movie (which was staying in theaters for one last day) in order to see her. Pissed off and jealous, he goes to Yanase's house to vent. The typical drama of this series. Then things take a turn for the worse when Hatori calls Yanase and Yanase says he's not handing Chiaki over. Yanase tries to confess to Chiaki a second time hoping he would take him seriously this time (and at this point, Yanase is desperate for Chiaki to return his feelings). By forcing himself on Chiaki, Chiaki retaliates by actually punching in the face (and mind you that Chiaki is the type of person that wouldn't hurt a fly) and the rejection finally causes him to break downcrying in front of his best friend. Naturally, what makes the situation worse is Hatori forcing his way inside the house and proceeding to beat up Yanase after he literally shut down and wasn't going to fight back. Chiaki stops Hatori in time and Chiaki literally treats Yuu the same as always as leaving, which leaves a bad aftertaste considering the fact that the episode ends with Hatori explaining why he was with his ex girlfriend in the first place and Chiaki forgetting what happened. A what the hell moment with Chiaki acting like nothing happened? Sure. A Karma Houdini for Hatori in this episode? Definitely. Yanase is just that unlucky.
Shin Mazinger had Wham Ending. In the last episode Kouji finally defeats and kills Doctor Hell. The same moment sky goes red, Crowning Music of Awesome suddenly stops and wierd thigs starts coming from the sky. It's then revealed that Doctor Hell had installed a program in Baron Ashura that prevented him from comitting suicide as long as Hell is alive. Now, after tricking Kouji into killing Hell for him, Ashura takes his own life, braking ancient seal and unleashing Mycean Empire, lead by Great General Of Darkness, on the world.
Episode 34 of Revolutionary Girl Utena, in which two meta characters interact with the main cast for the first time in the entire series, and in doing so casually reveal the entire plot and (almost) all of its secrets. Suddenly, everything that's happened up til then makes sense, and it's horrifying.
Not to mention episode 33, which features Utena having sex with Akio. In a clip show.
You're all forgetting the original WHAM episode - episode 23, wherein we learn huge chunks of Mikage's memories are fake. Nemuro burned down the hall, the real Mamiya died years ago, and Anthy was posing as Mamiya the whole time.
Episode 8 of Simoun. And 14. And 16. And... oh, heck, pretty much the entire second half of the series.
Sket Dance, 'Switch Off'. Kazuyoshi Usui became 'Switch' in memory of his late younger brother, who was murdered in confused circumstances Switch blamed himself for. Done in the form of a TomatoSurprise with the proceeding episode - Takemitsu reconciling with his younger brother, and Switch's reaction to it - going some way to mislead viewers about what happens.
'Ogress'. Himeko's backstory.
'Happy Birthday' and 'Happy Rebirthday'. Bossun's backstory.
'Switch On'. How Switch meets Bossun and Himeko.
Slayers is usually free of these, being more comedy-oriented. One notable exception occurs towards the end of Slayers Next, when Gaav survives Lina's Ragna Blade, then Fibrizo reveals himself and effortlessly kills Gaav. It's striking because up to this point Gaav had been clearly presented as the antagonist and Fibrizo does not appear in the opening credits (OK, he does, but you only realize this after The Reveal is pulled off). The series' tone shifts entirely after this episode as the humor is toned down and characterization kicks into full speed.
Episode 10 of Sola is this, when Matsuri reveals to Yorito that he's not a human, but rather a golem made of paper that Aono had made with her yaka powers and implanted with the memories of her dead brother, Yorito.
People were wondering if war would ever be shown in Sora No Woto, being a military show. It is, in Episode 7, and changes the view on one of the characters completely.
Soukou No Strain is another series where the first wham comes at the end of the first episode: Characters are introduced, and even hints of a romance is set up... Then the brother of our main character shows up and kills everyone.
Soul Eater: The episode where the Kishin is revived You know that this is a wham episode too, because after this arc ends and the new arc begins, you start to see less and less comedic fillers and more exhausting and BRUTAL battles in the series.
Chapter 87 Chrona kills Medusa. And in chapter 88 it ends with Shinigami's Wham Line ordering Spartoi to kill Chrona
Chapter 110 Kid gains his father's power, Shinigami-sama dies and on the very last page, the Kishin stabs Maka straight through her chest
Chapter 112 Crona attempts to become a Barrier Maiden to seal Asura...and the resulting wave of black blood either kills or traps Spirit, Marie and Sid.
Stellviaofthe Universe where in episode 11, Ayaka attacks Shima out of jealousy for her achievements, and episode 16, where people actually die, for the first time.
The attack of the Bodolzaa fleet — and its outcome — in Super Dimension Fortress Macross. Given how every other television show went during its time, NOBODY expected 90% of the Earth's surface to be reduced to ash.
In Suzumiya Haruhi, despite brief references to the supernatural, Haruhi appears to be an excessively Genre SavvyCloudcuckoolander who can't tell fantasy from reality... then comes episode five (chronologically third): Yuki, the girl who had just been sitting there reading when the club started, is an alien drawn to the planet by a cosmic disturbance three years before. Mikuru, whom Haruhi grabbed at random because she thought she was cute, is a time traveller there to understand the time travel threshold, three years before. Itsuki, who was inducted due to Haruhi's obsession with the idea of a mysterious New Transfer Student, turns out to be from a group of espers who gained their powers in a cataclysm three years before. What are the odds? High, once you learn that Haruhi herself is a godlike being, unwittingly responsible for all three phenomena. And there are nine episodes to go.
Technically the wham episode chronologically would have been Episode 4 (Broadcast Order Episode 10), where the Class President traps Kyon in an artificial world and tries her best to kill him to see what Suzumiya will do, only to be stopped by the aforementioned Nagato Yuki, wielding reality-overwrite powers. And then he meets Mikuru's future self. This is around the point where Kyon realizes he has to believe all these weird outlandish stories.
The first half of Tamako Market is a plain—if not downright boring—Slice Of Live. Then in episode 7 Choi arrives and chews out Dela for neglecting his duties. After a few misunderstandings (mostly the result of Dela trying to shift the blame for his idleness), she comes to befriend Tamako. At the end, she recognizes Tamako as her prince's destined bride.She is wrong, however.
Tenchi Muyo! gets one in OAV 3, Episode 6. After spending the past five episodes setting off conflicts and sitting back to watch, Zetto decides to take direct action against Tenchi, by BLOWING UP HALF OF EARTH. And I don't just mean half the surface, I mean all the way down to the core and back out the other side. And just to cap it off, after giving Tenchi a cheery "Yo", he waves his hand and vapourises most of the moon. This later reveals a slightly subverted Wham when Tenchi manifests himself as a god.
Before this, there was two in OAV 2. In episode 1, we learn about Washu's past and that the form we see her in ISN'T her true form. And episode 2, we find out Sasami's past.
Tengen Toppa Gurren Lagann. Episode.Eight. So you thought this series was just a fun, episodic romp, mmm? Well, here, the Plot Armor comes off, manly tears are shed, and Heroic BSOD ensues. From here on out, the show takes itself much more seriously, and so does the audience.
The fuel for the world and everything our heroes have been fighting for may eventually, should it continue to grow, kill absolutely everything in existence. And you thought the Anti-Spirals were just sociopaths.
The 10th of Tiger & Bunny ends with the long-awaited arrival of the Ouroboros organization, which introduces itself by taking the entire city hostage for the release of their leader. Episode 10 is then entirely dwarfed by the events of episode 12, where Kotetsu accidentally betrays the trust Barnaby was slowly developing in him... Right before Jake utterly destroys Kotetsu in a one-on-one match, sending him to the ICU in critical condition while Barnaby awaits his own fight with Jake. The fandom collectively suffered a massive nervous breakdown as soon as the credits rolled.
And now there's episode 16, which reveals that Kotetsu's longtime hero, Mr. Legend, was Yuri Petrov's father — Yuri Petrov's abusive father.
Every episode from 19 onward is a combination of this and From Bad to Worse. Observe:
Episode 19: It turns out that Maverick is the one who actually murdered Barnaby's parents. He tells this to Barnaby - right before wiping his memory with heretofore unknown NEXT power.
Episode 20: Maverick wipes the memories of most of the other heroes. Kotetsu is officially Unpersoned, blamed for the murder of Samantha, and the other heroes begin to hunt him down.
Episode 21: As Kotetsu is running for his life from his friends and co-workers, Lunatic of all people swoops in to save his life.
Episode 22: Kaede shows up as Little Miss Badass and cures the heroes of their amnesia...except for Barnaby, who ends up facing Kotetsu one-on-one.
Episode 23: Just as Barnaby remembers who Kotetsu is, it's revealed that the other heroes have been captured and hooked up to bomb collars a la Battle Royale
Episode 24: Kotetsu dies...
Episode 25: ... temporarily. He comes back to punch Maverick in the face. Unlike the sad or terrifying whams above, this one is awesome. There's also the fact that he finally decides to quit being a hero...for all of six months.
Every episode from 20 to 24 has an increasing magnitude of Wham.
The manga also has one at the end of the original's run, where Vash meets up with Knives. The results are similar to that of episode 17 of the anime.
Vol. 6 of Maximum has a giant Wham moment at the end. So, you know how Vash's hair is slightly blacker than it was in the original series? Turns out that it represents a Plant's lifespan and their hair darkens each time they use their powers. Every time Vash uses his skills he's been slowly killing himself.
Tsubasa Reservoir Chronicle exemplifies this in Acid Tokyo when we find out that Syaoran was really a clone of the original the whole time, and he proceeds to eat Fai's eye and have a big epic battle with his original counterpart. Then Kurogane gets Yuuko to turn Fai into a vampire so he can survive, and in return he is the only person Fai can feed on (Ho Yay anyone?) After that we find out that Sakura was also a clone, and then there's the whole "WTF" moment when we find out... Syaoran's his own father? And Sakura's... His mother? And Yuuko... Was actually dead the whole time, and Buttchin is trying to keep her alive?
Pretty much everything during and after the country of Recort. Kurogane's past, Acid Tokyo, Infinity and Fai's past are all very VERY much WHAM. Especially Fai. Go on and read his past, then reread the manga. That smile just doesn't seem the same anymore.
20th Century Boys uses this in full force when the Big Bad is murdered. Halfway through the series. As an extra jab they reveal his identity right after.
Urasawa had already done it once before, at the end of volume 5 when we learn that Kenji completely failed and the Big Bad controls Japan. He does it again at the end of volume 15 when we learn they now controls the whole world and the calendar now dates from his resurrection. Yeah, that's right: the Big Badreplaces Jesus!
In a way, episode 9 of Wandering Son. Takatsuki goes to school in a boys uniform. Later in the episode Doi meets Yuki and we learn she's a transitioned Transsexual. At the end of the episode, Nitori goes to school in a Sailor Fuku and wig. The manga has its fair share of Wham Chapters; chapter 31, chapter 32, chapter 54, chapter 63, chapter 66, and chapter 99 being the most prominent.
The anime of Welcome to the NHK has this for episode 13. Sato shows one of the first major signs of overcoming his hikikomori disorder when his senpai Hitomi (who he's very attracted to) seems to invite him on a vacation with her, but finds out that she has inadvertently taken him with her to a group suicide party AND has a boyfriend who proposes to her to convince her not to kill herself. This leads to him actually attempting suicide himself, since he was using her as motivation to change. In the chaos that follows, Misaki desperately attempts to save him, which leads to her showing the first real sign of her own issues. By the end of the episode the Misaki and Sato are so emotionally battered that they burst out in combined wails that carry on to the end title card.
The World God Only Knows FLAG 116 has two Whams in quick succession, following an earlier Reveal: that Kanon is the holder of the goddess Apollo, and thus remembers Keima. Wham One: Kanon publicly confesses her love to him. Wham Two: Kanon suffers a critical stab wound, marking a significant turning point in the series.
If that was not wham enough, then FLAG 165 to 168 should hit hard like an oncoming rig. In summary: Chihiro confesses her love to Keima; the latter gets confused as to how she came to like him even before her conquest; Ayumi is then revealed to actually have the last goddess; Keima is then forced to dump Chihiro, with Ayumi watching on, then later enters into a semi-Heroic BSOD state realizing the mess he entered himself into... Somebody say "Four-Wham-Pileup?"
Episode 12 of the X1999 anime: Kamui chooses to be a Dragon of Heaven, making Fuuma become a Dragon of Earth, and switch personality. After that, Fuuma throws Kamui into a wall, steals his sword, pins him to a wall with shards of glass, piercing his hand with the sword, licks his neck, and proceeds to crucify his own sister and kill her.
Yu-Gi-Oh! has a tradition for having their protagonists almost never lose a duel, so almost any episode where they do lose counts as this. One of the more notable examples is Yugi losing in Season 4 to Rafael. Unlike most of the villains and most of Yugi's past defeats, Rafael didn't have to cheat to beat him, he won fair and square. Sure, he forced Yami Yugi to play an evil card, but he did it by backing him into a corner so he had no choice but to use it, then took a pummelling and ultimately used Yami Yugi's more brutal and reckless personality against him to win. Cue Yugi losing his soul, Yami Yugi angsting, and and the season suddenly taking on a darker tone.
There's also episode 52... in the Japanese version. The dub gave away the big twist in the second episode (and for some reason the characters are all still surprised come episode 52).
The beginning of the Duelist Kingdom arc served as one in the manga. Although it served as the first episodes of the anime, reading the manga for the first time made it pretty damn shocking when Yugi came across the Duel Monsters creator who also turned out to be another wielder of the Millennium Items.
After two rather light-hearted seasons that got no more serious than the previous show, Yu-Gi-Oh! GX suddenly pulled season three on us, which got as dramatic as the end of the second season about ten episodes in. The really dramatic turning point, though, is the duel again Professor Satou where Judai starts to crack, we see a crazy guy with petty motives that aren't, quite. The first duel where Judai really isn't enjoying himself, and at the end Satou dies by falling off the bridge. And it only goes downhill from there.
Season 2 wasn't all light-hearted. Episode 65 comes to mind. Ryo, mentally and emotionally falling apart because of his inability to cope with failure, becoming trapped in an Underground arena, and horribly tortured into a truly disturbing Freak Out and Face-Heel Turn. His Kick the Dog in Episode 95 might count too.
Episode 107 of Yu-Gi-Oh! 5Ds. First, Bruno jumps off a cliff then becomes Dark Glass. He proceeds to duel Placido while Yusei gets magical cards from a giant obelisk that he teleported to. He proceeds to meet what may be God, and then goes back and takes over in Dark Glass's place. Then, Placido fuses with his motorcycle.
YuYu Hakusho Yusuke solves what seems like just another case...only to have Toguro, the supposedly dead hired muscle from that case, reveal himself to be alive and far more powerful than Yusuke could have imagined. Yusuke is thus forced to fight for his life in the Dark Tournament.