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!""
 * 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"