Technically shared by the narrator and Ryoma in Shin Getter Robo: "GETTER EMPEROR CHANGE!" ' The voice that quakes the Universe itself was, indeed, that of Ryoma Nagare.'' "CHANGE GETTER EMPEROR ONE!"
There's an interesting in-universe example in Angel Beats. Though the audience has the inkling that the disappearance of characters is not a bad thing, the main cast is completely clueless. Of course, after the events of episode 9, Otonashi muses that maybe disappearing from the world would be for the best... only to realize that Kanade agrees with him. Cue the awkward realization that the Big Bad of the series has been on their side the whole time
This exchange from Soul Eater, just as Crona is forgiven by Death for furthering the madness that was in Stein. Granted, this series has a lot after the halfway point.
Nygas: Medusa. Just what are you doing here?
Medusa: I'm not looking for a fight. I surrender.
The manga has the Great Old One of the Book of Eibon calling Death the Kid; a "fragment of Shinigami."
There's also the last line of Chapter 88, where the Spartoi kids find out that they've been ordered to execute Crona. Considering that the rest of Chapter 88 was a total filler chapter...yeah. Wham Line.
108. Dear Lord, 108. Asura reveals that he too is a fragment of Lord Death, effectively making him Kid's OLDER BROTHER.
Haruhi Suzumiya: "...that's why I'm going to kill you and see how Miss Suzumiya reacts!"
Mao: (to Suzaku) Get your hands off of me, father-killer!
R2 Episode 5:
Nunnally: Hello? Big brother? Lelouch, is that you. It's me, Nunnally; Can you hear me? I'm coming over there to Area 11 to be the viceroy. Um, is there something wrong? Lelouch, it's Nunnally, your sister!
R2 Episode 18:
Lelouch: Could that be the weapon Suzaku was talking about? ...Nunnally!
Chapter 104, what Father says summarizes the WHAM situation the best:
Father: For me to imprison God within my body required enormous energy. And the citizens of this country provided it for me.
Also, two chapters previously...
Roy Mustang: "I...can't see."
Even before that: Hawkeye talks with Mrs. Bradley, and learns that Selim is adopted from one of their relatives, Hawkeye asks if Selim is one of Mrs. Bradley tells her, "He's the son of some distant relative of my husband." Hawkeye remembers that King Bradley has no relatives, then encounters Selim and confronts him about what she's learned.
Selim: I am the first homunculus. My name is Pride.
And before any of these:
Bradley: "Just as you have the Ultimate Shield...I have the Ultimate Eye."
Chapter 97, after it was thought that Wrath was dealt with...
Bradley: Hello everyone. I see that everything has gotten quite out of hand during my absence. I am coming to personally take back control of my country, and put down this coup.
Mikado: I have neither the power nor wisdom to oppose a foe who won't listen to reason. You won't even give me time to try. And so...I'll rely on numbers!
From episode 10: I have all the pawns I need
Also, in the graphic novel when Simon suddenly punches Izaya in the face and says: Have you ever killed people? I have.
Grave of the Fireflies: After returning from buying food, Seita comes back to a severely ill Setsuko who is delusional and weak. He gives her something to eat and makes dinner, bringing hope that Setsuko would recover. Then, after Seita leaves the scene, leaving Setsuko to lie there with a hunk of melon you think she'd wolf down, he voices over the line: "She never woke up". After that...you pretty much know what happened.
Zaji: Your delivery is just as good as the record holder. And seeing how Gauche Suede isn't a Bee anymore, you're pretty much at the top.
Much later, Lag figures out what exactly is wrong with Gauche.
Lag: Ever since you woke up, the whole time, you've been lying to us. Everything you said about me and Sylvette...did you learn it all from the letter bullet I shot into you? I believed...the real Gauche had returned. I believed it. Sylvette believes it. But no. You're not Gauche! You're Noir!
After telling Aria about the true nature of the sun, Hodai Franklin begins talking about Gauche.
Hodai: Poor girl. That fellow who was precious to you? His heart...is now part of the light of the world. Yes...He'll never......be whole again!
Aizen: I'm sorry. You must have been worried. I'm really sorry. I'm sorry for hurting you so much. There was something I had to do. Thank you, Hinamori. Thank you so much. Goodbye.
Chapter 147: Vice-Captain Hisagi looks like he's defeated Fifth Seat Ayasegawa and lectures Yumichika that he should give up because there's no possible way for a fifth seat to defeat a vice-captain and dying in such a pointless fashion would be a terrible death for a member of the battle-loving 11th division. If Yumichika didn't hit the Wham Line quota with his reveal that he's only such a low seat by choice, his reveal that he's also hiding the truth about his zanpakutou surely does.
Yumichika: "What I show you now is completely confidential. Take a peek at the true power of my zanpakutou!"
Precia: I'll put an end to everything. To all the time this girl was deprived of when I lost her.. and also to the doll I created to play as my daughter.
"You want to know something nice? Ever since I made you...every single moment...I've despised you."
Bakuman。 Chapter 100: "PCP isn't going to get an anime."
Chapter 76: "I WANT TO QUIT TANTO!"
In Chapter 46, Azuki tells Mashiro that she’ll hate him if he doesn’t take time off work until he’s discharged from the hospital, but Mashiro, not believing her, refuses. She then apologizes and says "I've been in love with you for eight years, so how could I hate you?", which surprises him, as it is the first time he learns that she had always loved him.
School Days, final episode: Makoto has received a text message on his cellphone which just says "sorry," followed by a whole bunch of empty lines that scroll down, leading up to one word: "Sayonara." Cue seriousOh Crap.
The manga does this in spectacular fashion in the last chapter.
Kyubey (Episode 6): "I never would have thought you capable of throwing your friend off the bridge. That wasn't a sane act, Madoka!" note Madoka only tossed Sayaka's Soul Gem off the bridge, not knowing that it's a container for Sayaka's soul
Kyubey (Episode 6): "You people are all the same. I don't get it. Why do you people care so much where your souls are?"
Kyubey (Episode 8): In this country they call girls shoujo, and for girls who are growing up to be witches (majo), it's logical to call them "magical girls" (Mahou Shoujo).
Homura (Episode 8): I will not allow your plan to succeed, Kyubey...no, Incubator.
Madoka (Episode 11): Homura...I'm sorry.
Kyubey gets a lot of these. Practically every episode after the third has at least one Wham Line from Kyubey.
He's not the only one though:
Kyoko: (Episode 6): What the hell is this? [Sayaka]'s dead!
Madoka: (Episode 12): I want to erase every witch before they are born!
Seems like your memory is coming back. You were bound to find out sooner or later. Now you can take responsibility for what you've done with this planet. (towards Ohji) Isn't that right, Professor?
There's no need for two Suns. That is why I gave the order...for you to kill Luna.
Ore Imo manga, chapter 25: "I'M...DEEPLY IN LOVE WITH MY SISTERRRRRR!!" If you've read the novel or seen the anime, you'll know that things are cleared up, but since the manga chapter ends on a Cliff Hanger...
In the first Rebuild movie, there's the moment where Misato reveals Lilith's body to Shinji. A Wham Line because in previous incarnations she didn't know about the body until Kaji revealed it, and only knew it as Adam until Kaworu arrived. Thus raising questions about Misato's possible connection to Seele in this continuity.
Fuyutsuki: This is your mother...Yui Ayanami.
Going back to the original series, from episode 24, we learn the truth behind the AT Field:
Kaworu: "That's right. That's what you Lilin call it. The sacred domain where none may trespass. The light of the soul. Lilin, you know, don't you? That the AT Field is the wall that everyone has in their heart?"4
Earlier that episode:
Misato: The Fifth Child...what is he?
Ritsuko: He is probably the last Angel.
In Mai-Otome, John Smith admits that he can't take on a Materialized Arika, and so calls for help from The Mole.
Third Princess Carissa: “Begin the invasion. I now have Curtana Original, the sword that decides the king, within my grasp. This makes me, Carissa, the ruler of the United Kingdom. Anyone that does not want to see the country decay under the rule of the previous pacifist queen, stand up of your own will. To bring about the new United Kingdom, leveling some things will be necessary and some destruction will be necessary.”
In the Mai-HiME manga, Nagi is able to throw his foes into disarray long enough to attempt to escape with the following question.
Nagi: This may be odd for me to ask right now, but how did it taste...when you kissed Mai-chan?
In the anime, Shiho, with the following line, essentially admits to killing Takumi.
In the Ace Attorney manga, Edgeworth argues that Bobby Wolfe might have burned down the Den of Spiders if he intended to turn himself in or commit suicide, leaving no one to care for his spiders. Phoenix then argues that his friend Thomas Spitzer could have cared for them.
Edgeworth: Well then, why don't we ask him? I would like to call my next witness, Thomas Spitzer. (Cue Oh Crap from Phoenix as Spitzer testifies for the prosecution.)
Kokabiel: Seeing that even after losing the masters you serve, you devils and followers of God can still fight, huh?
Rias: ...What do you mean?
Kokabiel: Fuhaha, fuhahahahahahahahahaha! That’s right! I totally forgot! The truth wasn’t revealed to you lower guys! Then I will tell you. In the war between the three sides, not only the Yondai-Maou but also God died.
In episode 3 of Sakurasou no Pet na Kanojo, where Sorata tells Jin over the phone that he's made up his mind to really leave Sakura Hall instead of just dragging his feet about it. This doesn't sit very well with Mashiro, who overheard the conversation, and plays an important role in episode 4.
In Episode 8, as things look desperate for Oorai during their match against Pravda, Miho says that perhaps, losing may not be such a bad thing, since she made friends and rekindled her love of tanks. She then finds out the stakes are much higher than she thought.
Momo: What are you saying? Our school's gone if we lose!
In the Little Army manga, after having had a serious fight with Emi, Miho goes to her house to try to reconcile with her, and offer to challenge Maho's team to a tank battle, only to get a cold reception from Emi.
Emi's mother: Such a helpless child...you'll be separated soon, so you should make up.
Miho: Eh? What did you mean?
Emi's mother: I'm sorry, you didn't know about it yet, right? Actually, we are returning to Deutschland next month.
Also from Little Army, when Maho shifts from a Cool Big Sis to an Ice Queen, and also confirms that she did, as Emi said, take the opportunity to shoot down Emi's sister's team's flag tank when it went to save one of hers.
Kikuyo: Lady Miho, your current actions in Ooarai... the madam knows all of it.
Miho: I thought so...
Kikuyo: ...That I of all people has to inform you about such matters, I'm hesitant, but... In the semifinals... if Lady Miho happens to lose against Pravda High... Lady Miho... the Nishizumi houshold will... disinherit you.