In Good Omens, Aziraphale, an Angel, actually says a very emphatic "Fuck." just before he dies. Almost. It was the first such instance in 6000 years. More than one reader had to put the book down. Everything about the character is the antithesis of a curse, so a hardened Cluster F Bomber will still burst into shocked giggles. Incidentally, this is easily the most obscene moment in the entire book.
The book has also spent the entire time up until the actual swearing mercilessly hanging lampshades on the fact that he doesn't swear wherever possible, in lines like, "Oh dear," muttered Aziraphale with the practiced ease of one who has spent six thousand years not swearing ..." This helps to lend the appropriate amount of gravity to the moment whan it does occur.
Mostly Harmless, spoken by Arthur to Ford, at the end of the worst day of his [Arthur's] life.
The Narrator gets one in Chapter 25 of So Long, And Thanks For All The Fish in a tangent about the nature of Arthur's sexuality (read: if he actually had one):
"This Arthur Dent," comes the cry from the farthest reaches of the galaxy, and has even now been found inscribed on a deep space probe thought to originate from an alien galaxy at a distance too hideous to contemplate, "what is he, man or mouse? Is he interested in nothing more than tea and the wider issues of life? Has he no spirit? Has he no passion? Does he not, to put it in a nutshell, fuck?" Those who wish to know should read on. Others may wish to skip on to the last chapter which is a good bit and has Marvin in it.
This is especially effective because it's the first time the word "fuck" is said in the entire series. And this is in the fourth book, in a series that is remarkably tame (the worst language before that is the word "shit" ... once). But it really carries much more weight when Arthur says it in Mostly Harmless because he is normally impressively tolerant of Ford Prefect's nonsense up to this point. In comparison, when Ford says it later in the same book, it's done casually and no one is supposed to care.
Only in the American edition. Elsewhere, the word "fuck" first appears in the previous book, in reference to the award for "Most Gratuitous Use of the Word 'Fuck' in a Serious Screenplay".
Zaphod's use of "Belgium!" when they're in the ice cave in the original radio series is an example in-universe - he'd never normally use such strong language unless something was really wrong, and it prompts Ford to take the situation seriously.
Speaking of Belgium, the use of the word "Belgium" as an expletive is, in the books, established when Arthur runs afoul of a movie star who is extremely proud of having won an award for the most gratuitous use of such in a movie. There is a hilarious exchange revolving around Arthur trying to make sense of what's so offensive about the word Belgium..
Only in the American edition. Elsewhere...
"The Award for the Most Gratuitous Use of the Word 'Fuck' in a Serious Screenplay".
In Peter David's Star Trek novel Vendetta, a Federation ship (not the Enterprise) sees the Planet Eater doing its thing, and an Ensign swears and then he apologizes to the captain, since that's frowned on; but the captain says that, no, that's quite all right; that's really the best way to describe the situation.
In the Star Trek: Vanguard novel Precipice, a civilian character warned against helping a pre-warp culture fight the Klingons responds "Fuck the Prime Directive". Possibly the first use of the f-word in the entire Trekverse.
Marge's use is a subtler example, as while it makes sense literally, the other sense of the word is clearly implied as well. (Marge compares Harry's alleged behavioral problems and his mother's alleged similar traits to dog breeding, stating "If there's something wrong with the bitch, there'll be something wrong with the pup." As Harry realizes from the moment that came out of her mouth that she had aimed a Your Mom joke at him, the next plot points are promptly set in motion)
Up to Deathly Hallows, both Harry and Ron have used profanity at least once, but here, Hermione finally gets her turn to talk like a sailor, with such words and phrases as "damn", "complete ass", and basically the wizarding equivalent of "holy shit" (read: "Merlin's pants!").
In Misery the writer Paul is being held hostage by the insane fan Annie, who dislikes swearing and prefers using Gosh Dang It Heck nonsense-words when she is angry. Paul soon learns that despite how frightening and cruel she normally can be, he should be truly terrified of her whenever she actually swears.
In Heinlein's Starship Troopers, Juan Rico's first day of boot camp introduces Sergeant Zim, whose first act is to rant for several consecutive minutes on the various shortcomings (moral, mental, and physical) of the recruits, never once repeating himself or using profanity. Zim reserves profanity for when he's really serious. Rico spends most of the monologue wishing they had had someone with Zim's command of language on his debate team at school.
In the Watership Down novel, just as the heroes are about to attack the Warren of the Snares, Fiver, who is timid by nature, screams "Embleer Frith" — which translates roughly to "Damn God", to get them to stop.
Later in the book, Bigwig tells Woundwort to "Silflay hraka, u embleer rah" — this translates to "Eat shit, O Stinking King".
Though this may not qualify, as Bigwig isn't exactly the most timid of characters. In fact, this scene, while also qualifying for a Crowning Moment Of Awesome, establishes him as the biggest, meanest, most dangerous rabbit in the novel. Which is saying something, considering who Woundwort is.
Sam Vimes in Men at Arms screams, "[I'm] the LAW, you SONS of BITCHES!" while he's being possessed by the gonne.
Sam has another one in Jingo: "Guards are civilians, you inbred streak of piss!"
We get it again a few pages later, except this time he's mumbling it in shock, scarcely believing he said it - the person he said it to was a very high ranking member of the city and, if I remember correctly, he said it in front of the very, very imposing assassin leader of the city.
The Discworld books are pretty good at precision swearing, actually. When someone says "Oh, bugger," they really mean it.
Tallstar refusing Tigerstar's demands and publicly calling him a "piece of foxdung" ("piece of shit") in The Darkest Hour seems to carry more weight, being said by the stereotypically meek WindClan leader, and only makes it more of a Crowning Moment Of Awesome for him.
Robin Hobb uses the F-word only a very few times in her books, meaning each has maximum impact. Towards the end of the Realm of the Elderlings novel Ship of Destiny, after Kennith rapes Althea, her nephew Wintrow defends him, causing Althea to scream at him: "Fuck you, Wintrow!"
Luke Skywalker: [calms himself] Nothing. A bad word. Your mother won't be happy I said it in front of you.
Ben tends to throw profanity around fairly freely when in annoying situations (as long as there's no one around; all right, his parents are exceptions, but the point stands), but if it's not the kind of profanity you usually see in a Star Wars book (almost always mentioned in passing and not actually printed), you know something very bad happened. The last sentence of the leading quote for this page, which is best summarized as "Oh crap, the Sith are back" is about as profane as you can get while still staying safe for work.
In War And Remembrance, this word is only used once, by Janice Henry to a Japanese grocer right after the Pearl Harbor attack.
Queen Elizabeth III uses "cluster fuck" to describe her feelings on Solly Admiral Byng's idiocy at New Tuscany in Storm from the Shadows.
In Contact, Ellie Arroway typically sticks to "Holy Toledo!", but after the Very Large Array finally picks up on what looks like a genuine message from extraterrestrials, she takes a moment to retreat to her office, closes the door behind her, and whispers "Holy shit!"
In The Girls Guide To Hunting And Fishing, the main character works for an annoyingly put-together, professional, well-educated type, and mentions that all this makes hearing her Precision F Strikes like seeing a strong man cry.
Inverted in the Shadowrun novel Night's Pawn, where the main character's occasional use of the word "fuck" has such an impact because he's the only person who still uses such an antiquated swear word. A member of the opposition even calls it "quaint".
In Fragment, the President of the United States gets one of these, when the Henders Island natives appear on screen, revealing that a nonhuman race of intelligent beings exists and has befriended the camera crew.
In one of the Garrett, P.I. novels, Garrett is startled when his friend Morley says "Shit!", as Morley doesn't often use non-elven profanity. Circumstances, however, make it appropriate, as a carnivorous dinosaur just stuck its head in the window of the coach they're sitting in.
The only occurrence of a swear word stronger than "hell" or "damn" in The Bartimaeus Trilogy (and those were used pretty sparingly too) was when a minor character called Jane Faraar a bitch, which she takes as a compliment. (Fitting considering she's a werewolf, or at the very least, runs a team of werewolves.)
In the Temeraire novels we have a book and a half of swear words no stronger than damn or hell and then suddenly we get the line "Fire, fire you fucking yellow-arsed millers!"
The Dresden Files is rarely very shy about a few swears here and there, but some characters are less prone to bouts of language than others. In The Warrior a short story from Side Jobs Michael, a devout catholic man who has never in the 12 main books of the series said so much as hell or damn—and has repeatedly reproached Harry for using same—delivers the line: "The son of a bitch hurt my little girl." Coming from him, it's so shocking that even Harry is taken aback.
When Harry really, REALLY needs Molly to shut up, he does this. He also slags trashcans and brings a small ball of plasma up to her face with the stated intention of keeping right on going, but it was probably the swearing thing.
Inverted in Cold Days which probably has more uses of the word in a single chapter than in the entire rest of the series to that point. Possibly another sign of the detrimental effect of the Mantle of the Winter Knight on Harry?
To be fair (at least in the example I'm thinking of), Harry had just come face-to-face with a monster that he'd barely survived, had only been driven off by a wizard far more powerful than him, and had only been killed (in Harry's knowledge) by a nuclear explosion.
In Gun, With Occasional Music, the First-Person Smartass narrator ends one chapter, when he's just figured out something vital about his case, with "It was time to quit fucking around."
While the Nightside series doesn't exactly shun profanity, one stellar example of this trope appears in The Good, The Bad And The Uncanny, when Walker has the gall to speak approvingly of duty and responsibility to a woman who's lost all three of her sons to duty, one way or another. She tells him to fuck off, and John Taylor nearly bursts into applause when she does so.
In Crysis: Legion, normally mild Dr. Gould decides that the best analogy to describe the Nanosuit's intended purpose against the Ceph is gay rape on hanging flies. It Makes Sense in Context, but everyone in the vicinity, even the moaning-in-pain wounded, is Dumb Struck.
In the 4th Kingdom Keepers novel, Wayne says "Damn" while demanding to check if Maleficent has escaped her cell at the end of the book. This is coming from a novel where no curse has ever before been written and rarely implied and "OMG" is stated out loud in place of the more blasphemous alternative.
In Marilyn French's The Women's Room, Mira - in contrast to other members of the group - swears so little that the group find it hilarious when she tells them to 'go fuck themselves', which she sees as passing a sort of initiation test. Ben realizes just how angry Mira is with him when she screams, "FUCK OFF, BEN!"
Xenocide (from the Enderís Game series) by Orson Scott Card has a select few swears, particularly a conversation between Miro and Jane.
Miro: I thought you were my friend.
Jane: I am. I can read your mind.
Miro: You're a meddling old bitch and you can't read anything.
In Septimus Heap, in Syren, when Septimus is trying to get a Sealed door open to rescue people trapped behind it:
Septimus: I'll have to do a reverse ... not so easy without a Darke talisman. Rats
Prince Roger: Captain Armand Pahner's every word is precision strike, so whenever he does swear, it is fucking surgical. And you know the fecal matter has most definitely hit the pneumatic impeller.
In the Stephen King novella The Body (later filmed as Stand by Me) 13-year-old Gordie is neglected by his parents, who are lost in a fog of grief since his brother died. One day his mother is dreamily reminiscing about the brother on a day when Gordie's been through some severe stuff and his response is, "Yeah, that's a real bitch." His mother doesn't notice.
The Great Gatsby: Owl-eyed man's funeral oration briefly conveys Gatsby's sad life and death.
"The poor son-of-a-bitch," he said.
Roald Dahl had a tendency to insert the occasional mild vulgarity into his stories:
Philip Larkin's infamous poem "This Be The Verse" starts off with "They fuck you up, your mum and dad." (there is a second F-strike in "But they were fucked up in their turn...")
The Bible, in the original Hebrew, contains one in 1 Samuel, when King Saul figures out that Jonathan is actually trying to assist David. The Living Bible, for instance, translates Saul's harsh words thus:
Saul: You son of a bitch! Do you think I donít know that you want this son of a nobody to be king in your place, shaming yourself and your mother? As long as that fellow is alive, youíll never be king. Now go and get him so I can kill him!
In a New Testament example, the Book of Acts includes an instance where someone tries to offer Peter money for a place in a then-new faith now known as Christianity. The Message offers this translation of Peter's quick rebuke:
Peter: To hell with your money! And you along with it.
In Dave Barry in Cyberspace, a series of commands in English are typed into a DOS prompt in a vain attempt to get the computer to do something except print "BAD COMMAND OR FILENAME". Until:
A:> F**K YOU BAD COMMAND OR FILENAME, A**HOLE
The title character of the E. E. Cummings poem "i sing of Olaf glad and big":
A spanish translation renders that line as "Metanse al jodido jeep!" which translates to "Get in the fucking jeep!"
Up to Professor Coleís lecture, Murderess comes across as a fairly tame and rather typical teen drama novel with some fantastic elements. As soon as Lu tells him her last name, however, things take a turn for the darker, and he openly calls her a bitch.
In The Last Ship, Thomas, a very prim gentleman, delivers one of these when several other characters begin arguing with each other.
"And if everyone did, is anyone suggesting we start some sort of fucking treasure hunt to find as many of those pockets as we can before our fuel runs out and we end up wallowing in some sea somewhere?"
In Sweet Valley Confidential, a disastrous dinner party chapter ends with mother Alice hollering, "Ned! Bring out the fucking cake!" Nope, this is not your little sister's Sweet Valley.