Wham! Line/Comic Books

"Veidt: "Do it?" Dan, I'm not a Republic serial villain. Did you seriously think I'd explain my masterstroke if there was the slightest chance of you affecting its outcome? I did it thirty-five minutes ago."
 * The final line of chapter 11 of Watchmen.

"Nite Owl: Rorschach, I think we're in bad trouble. The person behind this, the person we're up against... I think it's Adrian."
 * Also while Nite Owl and Rorschach are looking through Ozymandias' office for clues about who might be targeting heroes, having been unable to speak with Ozymandias themselves.

"Mary Jane: You don't have to make up another one of your phony excuses, Peter! Not now--! I know the truth! The real truth! Peter: What are you talking about? Mary Jane: I've known your secret for years! Up until now, I've always thought I could cope with it if I ever had to experience it firsthand -- but I can't! I can't! I just can't cope with the fact that Peter Parker is secretly Spider-Man!"
 * One Hundred Bullets #91: "Rothstein is dead. The connection is cut. No more attaches, no more Revenge, no more hundred bullets. Graves' game is over."
 * Cerebus: "Something fell..." The second time this line is spoken, you experience the author's schizoid break. Wham.
 * Transmetropolitan: One percent.
 * Blackest Night: Thaal Sinestro of Korugar. Destiny awaits.
 * Planetary: I'm the Fourth Man.
 * House of M: "No more mutants."
 * Punisher: Born: "YES."
 * The Amazing Spider-Man # 248, "The Kid Who Collects Spider-Man." "You see, Tim has leukemia and the doctors give him only a few weeks to live."
 * Another Spider-Man example with a huge impact on the entire mythos and which comes as a revelation not just to the readers, but to the protagonist as well, from The Amazing Spider-Man #257:

"Fabian Cortez: "How could I possibly lose the points for Magnus's death, unless…?" (eyes widen) "NOOO!""
 * In the same vein is Aunt May, on her deathbed, asking Peter what it's like to be Spider-man. Despite a very positive reception to the death and massive Plot Holes required to retcon it, it was retconned to add yet another level of confusion to the Clone Saga. Despite the retcon in the mainline comics, it remains canon in MC2.
 * Batman The Long Halloween: "I am Holiday."
 * X-Men #300

"Knives: He cheated on us, Ramona. Both of us."
 * The first issue of the Joss Whedon run on Astonishing X-Men closes on a lecture that doesn't sound anything we haven't heard before, and then the last line turns it around completely: "They've been called angels and devils...they've committed atrocities, and been victim to atrocities themselves. They've been labeled monsters, and not without reason. But I will tell you what mutants are. Mutants are people. No better or worse by nature than anybody else. Just people. People with a disease. Mutants are not the next stage in human evolution. They are not the end of mankind. The mutant gene is nothing more than a disease. A corruption of healthy cellular activity. And now at last...we have found a cure."
 * A fairly mild example, as the announcement made in the final line was not something X-Men readers had not seen before, e. g. during the Kelly/Seagle run.
 * A few in Jack Chick's tracts:
 * The Letter: "Mildred... didn't you hear? Saturday night Frances and Paul's car skidded in the rain and they hit a tree. John's still alive but Frances died instantly."
 * Baby Talk: "She's not there. Thelma took her to the clinic. They left an hour ago."
 * The Trial: "When Annie told me I should ask Jesus into my heart, I did!"
 * Scott Pilgrim has two in book 5:

"Ramona: (to Scott) Good job. Great. You actually made me think that you were a decent person. But you're just another evil ex waiting to happen, aren't you?"
 * And later:

"Kim: Simon? The guy from high school?"
 * In book 6, when Scott talks to Kim about the past, and she reveals that :

"''' "Come to me, children. Come to " Wolverine: "Negative. The Marauders don't have the baby. An took her from Cooperstown." Cyclops: "Charles, you trained me, Let me do my job." Future Mutant: "Yeah. You'll live. Leastways...until something else kills you." Mystique: "I've always been good with children." Rockslide: "We deserve a piece of the ac--...tion? ""
 * Preacher (Comic Book): Mom?
 * "Herr Starr? Your time is up, Herr Starr."
 * Batman and Robin #12: "They're all jokes."
 * The Sandman: "He's going to have to kill her."
 * "I've quit."
 * War of the Green Lanterns: "Thaal Sinestro of Korugar. You have the ability to overcome great fear. You have been chosen. Welcome to the Green Lantern Corps."
 * Suicide Squad: "Frank Rock died in 1945."
 * This one's especially painful. It was supposed to kick off a new story arc, but the series was cancelled prematurely, which caused it to be the last line in the series.
 * Flashpoint: "What did I do? Oh, Barry. My idol. My inspiration. That's the beauty of all this madness. I didn't do anything. Not a thing. You see, it turns out... You're the villain today."
 * Marvel 2099: "Thor is dead. I know. I was there."
 * Incredible Hulk #600: "The Good Doctor is out. The Bad Doctor is in."
 * Animal Man #15: "I can see you!"
 * Punishermax: "I want a divorce."
 * The last page of Ex Machina #1: "If I were a real hero, I would've been in time to stop the first plane."
 * X-Men's Messiah Complex is practically built on this.

"Alex: "I just have to do one thing first." Karolina: "What's that?" Alex: """
 * Oh god, Runaways.

"Xavin: "Chase... ran away. ""
 * The end of the "Parental Guidance" storyline.

"Batman: [to the New Joker]] So... it's you..
 * The Dark Knight Strikes Again
 * undefined"