Are You There God? It's Me, Margaret.: Margaret's father Herb cuts his finger trying to mow the lawn, enough that the blood seeps through the towel he wraps it in and he has to go the hospital. He ends up with eight stitches in his finger and has to hire local teenager Moose to cut the lawn.
In The Boy from Aleppo Who Painted the War, a soldier shoots off two of Adam's fingers for disrespecting him. Adam is grateful that at least it wasn't his drawing hand.
In Breakfast of Champions, Dwayne Hoover goes on a rampage and bites off part of Kilgore Trout's right ring finger.
Ciaphas Cain: In the story "Echoes of the Tomb", Cain is hit with a glancing shot from a Necron weapon that disintegrates two of his fingers. He has them replaced with augmetics.
In The Cobra Event a character's finger is contaminated with the virus and they must make a (very hasty) Life-or-Limb Decision. IIRC, they hesitate, and get infected anyway.
The second book of the series, The Drawing of the Three, opens with Roland having the index/middle fingers of his right hand cut off and eaten by a lobster-like creature. Made worse by the fact that his combat style up to that point was to dual-wield revolvers.
Even worse is near the end of the final book when Roland has to pluck one of the magical roses of the Dark Tower's field, whose thorns are extremely sharp. By the time Roland gets one in his mangled right hand, the palm has been deeply cut and one finger is still attached by only a single tendon.
Deltora Quest has monsters called the Granous who, when they capture a prisoner, force them to answer twenty riddles/logic puzzles. Every time the victim answers incorrectly or fails to answer within the allotted time, they bite off a finger. When they run out of fingers, they start on the toes.
In Thomas M. Disch's "Descending", the main character finally makes it to the bottom of an apparently endless series of down escalators, way past the exit level, only to discover that the up escalator is out of order. He promptly has a mental breakdown and sticks his fingers under the bottom treads of the down escalator.
In Dinner at Deviant's Palace by Tim Powers, the protagonist mashes his right hand between two heavy objects to fend off a psychic attack, breaking several fingers; two fingers subsequently have to be amputated.
In Making Money a character wears a ring that is much too small for him. His finger gets infected, starts to rot, etc., and eventually gets burned off by Applied Phlebotinum (which probably saves his life). Much too small for him and made of a dangerous metal. There's a reason the real Lord Vetinari doesn't wear the signet constantly.
Detached fingers are a common nuisance for zombie Reg Shoe, whether while shaking hands, playing the guitar, or feeding bits of meat to Buggy Swires' trained buzzard.
One of Bungling Inventor "Bloody Stupid" Johnson's few functional inventions is large, automatic potato-peeling machine currently employed in the Unseen University's kitchen. It was intended as a manicure device.
Doc Savage: In The Annihilist, Leo tortures Sidney Lorrey: starting by pulling fingernails out with pliers, and then moving on to whittling his fingers down to the bone with a sharp knife.
Doglands: At the start, Furgul and his sisters have to escape a cardboard box or they'll be killed. When the Gambler tries to push Furgul back into the box, Furgul bites off his thumb.
Dragonback: Someone threatens to burn Jack's fingers off one by one in Dragon and Thief. Jack retorts that they're trying to be quiet, and he wouldn't be able to keep from screaming if they did that.
In Dragon Bones the villains torture Ward's younger brother Tosten, to get Ward to tell them what they want to know. Among other things, they break his fingers. Particularly heartbreaking because Tosten is a harpist and really needs his fingers intact.
In the sequel Tisala is tortured by having strips of flesh removed from her hand - the wound gets infected and starts to grow necrotic. Luckily the heroes have a talented healer on strength.
Palin from Dragonlance is tortured in an attempt to find out why the mages magic is failing them. His fingernails were pulled out over and over each time they regrew, and his fingers were broken dozens of times. This hits especially hard as hands are considered an important part of spell casting. Even worse, he didn't know why the magic was waning, and therefore did not have a cop-out. He was tortured for years.
In The English Patient, David Carravaggio is described as "the man with the bandaged hands" because the Germans captured him and cut off his thumbs. The movie has this in a flashback scene.
In the novel Even Cowgirls Get The Blues the main character has one of her oversized thumbs amputated and a finger moved into the thumb position.
Experimental Film: When Lois is crawling on her hands and knees during the fire at Ursulines Studio, a man steps on her hand, breaking her finger. She keeps crawling with one hand.
In Fate/Zero, Sola Ui subjects her fiancé Kayneth to this to force him give her the Command Spells that will let her become Lancer's Master.
Damage to the digits seems to be one of Glokta's preferred methods of torture, notably used near the end of the trilogy when he chops off all of Severard's fingers on one hand, joint by joint. Glokta himself, on the other hand, is intimately acquainted with damage to the toes.
Though not gory, the descriptions of Craw's constantly-chewed fingernails in The Heroes are unpleasant.
In Forced Perspectives by Tim Powers, a gunman working for the villain has his gun blasted out of his hand during a fight with the hero. Several of his fingers are seriously injured; his boss refuses to let him get them professionally patched up, because that would lead to official attention they can't afford, and anyway if their Assimilation Plot works physical injuries will become irrelevant. The condition of the fingers worsens over the course of the book to the point that they're decaying and need to be amputated.
In Friday the 13th novel Hate-Kill-Repeat, marketing executive Tom Sheridan loses half the fingers on his left hand when deflecting an attack by Jason Voorhees. Fortunately, main character Halo Harlan is able to draw Jason off before he can do more damage, and considering what Jason usually does to people, Tom can consider himself "lucky" that he just lost a few fingers.
In the backstory of The Girl from the Miracles District, Nikita had two of her little fingers cut off by her father so that he could send them to her mother as a taunt.
Dennis Lehane's The Given Day has someone lose a finger during a gunfight.
In John Varley's The Golden Globe, the narrator slices off the thumb of an assassin after him. With a chainsaw. He keeps it in a thermos of dry ice. This might be partly revenge for the fact that the assassin had sliced off the fingers of a violinist friend of his.
In the Goosebumps book It Came From Beneath the Sink, protagonist Kat brings the Grool her dog found underneath the kitchen sink at her home to school to show her teacher, who ends up getting all her fingers broken after the drawer of her desk crushes hard against them.
In a rare example where the good guys play this trope, the trick to defeating a grindylow in the Harry Potter novels is to break its long, slender fingers when it tries to drown you.
The Heir Chronicles: In The Wizard Heir by Cinda Williams Chima, Seph gets the tips of three of his fingers cut off to attempt to blackmail his father into coming to get him from where the Big Bad is holding him hostage.
The second book of Phillip Pullman's His Dark Materials trilogy, The Subtle Knife, who apparently marks its next wielder by cutting off the pinky and ring finger of the left hand.
In The House of the Spirits, Villain Protagonist Esteban Trueba does this to Pedro Tercero Garcia after finding out that he's the lover of his daughter Blanca. While attacking the poor dude in a blind rage, he manages to sever three of his fingers with a hatchet. It poses huge trouble since Pedro Tercero is a gifted guitar player, but after an Heroic BSoD he then learns to play guitar without these fingers out of sheer willpower, and becomes a very famous performer.
James Bond: In the novel Live and Let Die, Mr. Big's henchman Tee-Hee breaks James Bond's left little finger by slowly bending it back until the bone snaps. It gives Bond occasional trouble throughout the rest of the story.
Joel Suzuki: In Mystery of the Moonfire, Joel loses all the fingers on his right hand to a Portal Cut. Fireflower rushes him to the Wavemaker temple, where Auravine's magic is powerful enough to regenerate the missing fingers.
Keeper of the Lost Cities: In Neverseen, the Black Swan say they'll have to freeze off Gethen's fingernails to remove the tracker substance from them, disturbing Sophie enough to enter her nightmares. They later assure her the process was painless and that they'd only made it sound more painful to frighten him.
In Firestarter, Andy comes home to find wife Vicky's corpse — with her fingernails having been pulled out (apparently with pliers or similar) by her killer(s).
The Nightmares & Dreamscapes short story "The Moving Finger" has the protagonist try to get rid of a finger living in his bathroom drain by dissolving it with industrial drain cleaner (it intentionally doesn't make sense in context), before cutting it off with an electric hedge trimmer.
In "Crouch End", also from Nightmares & Dreamscapes, there's a Sergeant Raymond, who enjoys breaking the fingers of pickpockets one by one.
"Sometimes They Come Back" perhaps contains the most squicky example of this trope. Jim Norman offers his right and left index fingers to a demon in exchange for helping him kill the teenagers responsible for the deaths of his brother and wife. The text describes him chopping them off in excruciating detail.
The Laundry Files: In The Fuller Memorandum, people who are or have recently been possessed by the soul-devouring entity known as TEAPOT will attempt to eat their own fingers.
During the climax of The Return of the King, Gollum bites off Frodo's finger with the Ring still on it, then falls into the volcano still holding said finger.
That's also how Sauron got defeated at the end of the Second Age when Isildur cut his ring-bearing finger.
The Lunar Chronicles: In Cress, Scarlet is glamoured into cutting off her own little finger while being interrogated on Luna.
Come Reaper's Gale, Feather Witch has a penchant for stabbing people in the eyes with fingers she took from dead guardsmen.
In book eight, Toll the Hounds, there is a serial killer roaming the city of Darujhistan whose weapon the guards cannot figure out. It turns out he has lost all of his fingers at some point in the past and uses his hands as clubs.
In the short story "Man from the South" by Roald Dahl, the narrator witnesses a bet where a boy will gain a brand new Cadillac from a man if the boy wins but will have his little finger cut off if he loses. The bet is halted when a woman comes in revealing that the man owns nothing — she won everything from him. She only has one finger and a thumb on her right hand — and the original bet started as the little finger of the left hand.
The main villain of The Mental State likes to amputate his minions' fingers every time they disobey or defy him, starting with the least important and working his way up. He gets a taste of his own medicine when the protagonist arranges a scenario allowing where by his own fingers end up being cut off. He spends the rest of the story wearing metalic prosthetic fingers.
In Miracle Creek, Matt badly burns his hands trying to help Henry and Kitt. The index and middle fingers of his right hand have to be amputated, his nails are all lost, his fingerprints are melted away, and the nerves in his fingertips are destroyed, so he can't feel anything with them now.
In Misery, sometime during the later half of the book Annie cuts off one of Paul's thumbs. And then puts it on a birthday cake and serves it to him, making a not-so subtle threat to force him to eat it. "Special candle," indeed.
Towards the end of the last Mistborn book, Vin's fingers are broken one by one by a Steel Inquisitor.
In Moby-Dick, Ishmael makes a passing reference to the sailors working in the blubber room of a whaling ship, who sometimes cut off a toe if they slip while chopping up the blubber.
In Neverwhere, Richard gets his finger broken by Mr. Vandamar under torture. Later, after he returns to London Above, one of his coworkers asks about it, but then writes it off as his own clumsiness, saying he " probably just slammed it in a door or something".
Jamie's fingers are broken with a mallet as prelude to a sadistic rape scene. Claire gets to break them again before she's able to reset them. And they still heal badly, so every so often they'll break again.
That's not to mention the fact that Jamie's hand is nailed to the table, and once he's released, he presses his mangled fingers to the table so the excruciating pain will keep him awake to bargain with Randall.
By one of the later books, An Echo in the Bone, Jamie is fed up with the problems caused by his rigid ring finger on that hand, such that when the tip is severed and his hand further mangled by a sword blow at the Battle of Saratoga, he has Claire amputate the offending digit entirely.
Big Kat from Peta Lyre's Rating Normal is a recovering heroin addict. Once she got into a fight with a fellow addict, who bit off her little finger. Now all she has is a stub that moves.
A Prayer for Owen Meany: Johnny is desperate to avoid the draft. The army won't draft people who're missing their trigger finger. Owen has access to a diamond saw.
The Radix: During the Cold-Blooded Torture Adriana Borgia rips Wurm's fingernails. Bonus squick when we find out she was his daughter and knew it.
Red Moon Rising: Prior to the story, Rae got her pinky finger amputated. She later cuts off the tip of a man's finger in a fight.
The Reynard Cycle: The fingers of Reynard's left hand are broken during a fight with a Chimera in The Baron of Maleperduys. Later, a mercenary steps on said hand and twists his heel.
In Ritual by Graham Masterton, a restaurant reviewer's teenage son becomes entangled in a strange cannibalism cult. His father, desperate to rescue him, has to infiltrate the cult by pretending to be interested in joining. To prove that he is genuine, he has to cut off a little finger, fry it, and eat it - and he does get to eat at least part of it before becoming too nauseated to continue. That he is willing to do this shows the level of desperation he is in to rescue his son. The cannibalism of the cult plus the father's profession of restaurant reviewer both contribute to a weird and grotesque food theme running through the entire novel, which Masterton (as one would expect) plays to the hilt.
Occurs in the 1939 novel Rogue Male, when the protagonist is captured in the midst of a mock assassination of an unnamedEuropean dictator. The authorities loyal to said dictator take a dim view of such shenanigans, and inflict a number of tortures upon him, including the removal of all his fingernails.
Roys Bedoys: In “That’s Dangerous, Roys Bedoys!”, Roys slams his fingers in the door.
In Norma Fox Mazer's Saturday The Twelfth Of October when Lisham dies, Farwe and Burrum have the tip of one of their fingers cut off as a sign of mourning.
The Science Fiction Weight-Loss Book (1983) anthology edited by Isaac Asimov, Martin H Greenberg, and George R R Martin has a story in which if a person reneges on their agreement (related to losing weight), a finger is cut off.
This may be "Quitters, inc" by Stephen King, where the eponymous organization enforces good habits through threat of corporal punishment, including loss of a spouse's finger for not losing weight.
Shatter the Sky: Sev has his fingers broken whenever he lies when he's being questioned by the emperor as a form of torture. He gets threatened with them being severed entirely too if he keeps lying.
The Sherlock Holmes story "The Adventure of the Engineer's Thumb" features a client who loses a thumb to an attacker with a meat cleaver. The resulting injury is gruesome even by Dr. Watson's standards as an army surgeon.
The Two-Faced Ring nearly squashes the thumbs off of anyone trying to wear it. Oh, and the only way to get it away from someone once they've put it on.
Septimus's thumb starts to inflate like a balloon after he's bitten by a spider in the Wizard Tower Library.
In Dave Duncan's The Seventh Sword series, thumbs are cut off as a way to remove a swordsman from office permanently. (Swordsmen act as police, judge, etc.) Though Nnanji prefers to give them a choice between the right hand and the head.
In Shackled by Ray Garton, a journalist is investigating a group of very nasty people who kidnap and abuse children in Satanic rituals, sex abuse, and worse. And these people will stop at nothing to protect themselves from exposure, and the journalist finds himself captive at their hands and is required to give them information that will betray those he is working with and trying to help. One of the methods they use involves snipping off his fingers one by one, joint by joint, giving him a further chance in between each one to give the required information. He finally caves in after losing most of his fingers, but not quite all. In a writer as intensely vivid and descriptive as Garton, this episode makes amongst the most squirm-producing reading one is likely to encounter.
Davos had the tips of his left fingers chopped off for his history as a smuggler.
Ramsay again. Donella Hornwood is locked in a tower and left there. She's found dead with her fingers chewed off.
When greyscale hits, it takes the fingers (and toes) first. Tyrion has to prick his fingers regularly to check for it - but at least that's better than Jon Connington, who debates whether or not he should cut off his fingers because he does have it.
The ironborn have a game called "the finger dance," which is basically two-man axe juggling. It's so called because participants frequently lose fingers.
A healer tried to sew Urrigon Greyjoy's fingers back on after he lost a round of the aforementioned finger dance, causing them to get infected and ultimately killing him.
In the first Song of the Lioness book, when Alanna has just arrived at the palace and is being told about the Initiation Ceremony she will have to go through at the end of her training for knighthood, Duke Gareth shows her a missing finger and says, "I lost this in the Chamber of the Ordeal." Word of God is that he actually lost it in a totally unrelated accident and just says that to make an impression on the new pages.
In the Spider-Man novel Goblin's Revenge, when Carnage escapes from prison he cuts off an unlucky guard's hands and then uses them to "wave goodbye" at the wounded guard.
Played with in Starburst, when celebrity violinist Angelique is concerned that an accident has left her hand so injured that she will never be able to play the violin again. However, her new boyfriend Jamie and a doctor are able to provide her with some simple techniques that help her regain feeling in her fingers a couple of weeks after the accident.
Star Wars Legends: The Truce at Bakura, right at the start, has Wedge Antilles manually prevent a messenger drone's self-destruct by going out into vacuum in a suit and putting his hand between components. His hand is horribly mangled and he almost dies of that and the cold before Luke saves him. Star Wars medical tech being what it is he ended up fine, but years later his hand gets twitchy when he's out in zero-g for any length of time.
In The Storm of M, Katje breaks two of Gerald's fingers while she's in labor with their daughter.
The Sum of All Fears, by Tom Clancy, has John Clark interrogating a pair of Arab terrorists after a nuclear bomb detonates in Denver, Colorado, and uses breaking the fingers of one of them to get information to help track down those responsible for the attack. In a rare aversion of the trope, it doesn't work, and they lie about who their backer was.
In Tales of Kolmar, Lanen's hands and arms are horrifically burned when she helps one of the Kantri with a difficult birth, and only the work of an expert healer and a friend feeding her lansip fruit let her use them again. The friend can't bring herself to describe it, but apparently, there wasn't much left but bone. In the next book, Berys has to cut off one of his own hands as payment in order to summon the Demonlord.
Tempest (2011): During one of Sabyn's meals with the captive Tempest, he asks her to pass him a drink. The Anti-Magic drug she's on has the side effect of making her sleepy and slow, and when she doesn't comply quickly enough, he starts violently beating her. He finishes off by stomping on her left hand, dislocating four fingers.
In There Is No Antimemetics Division, the disciples of SCP-3125 often maim the eyes or hands of the unconverted, including the right hand of Adam Wheeler.
This Alien Shore: When Ian Kent is found dead, his hands have dug into the floor, sending shards under his fingernails and turning them into a bloody mess.
In The Three-Body Problem, 3-Body players are dehydrated and placed in storage to survive their planet's "Chaotic Eras" in a parody of the Trisolarans' Bizarre Alien Biology. One player had his hand gnawed on by a rat while his skin was in storage and, when he was returned to normal, found what was left of his finger bleeding profusely.
In Three Days to Never by Tim Powers, one of the characters has occasional premonitions. The first time he has one, during the Six Days Wars, he immediately tests it by reaching out a hand to do the thing the premonition is warning him not to do — and a stray bullet takes one of his fingers off.
During the climax of The Three Hostages, the hero loses parts of a thumb and two fingers when the villain shoots his gun out of his hand.
In Guy Gavriel Kay's novel Tigana, true wizards bind themselves to the land (and thus gain power beyond the most basic magics) by severing the ring and middle fingers of one hand.
In the final Time Scout: Good going, bad guy, you just dipped your hands in molten bronze.
In the first Tribe book, when Spencer and the tribe are done with Spencer's latest "test" in wood shop, Peashooter decides to test Sporkboy's reflexes by turning on the table saw. He ends up slicing off the tip of Sporkboy's finger.
Robert Low's Viking novels feature a specific and very sharp knife used by Einar the Black and later Orn to interrogate prisoners by cutting their fingers off one at a time while they are hung upside-down from the Fjord-Elk's mast.
Wicked: Right after birth, Elphaba bit her midwife's finger off. It turns out that she had been born with sharp teeth.
In The Witcher saga, one of the villains dies on a frozen lake. When the ice breaks he holds desperately to the edge of the hole, trying to pull himself up until Ciri ice-skates over his fingers.
In Roald Dahl's The Witches, the protagonist's grandmother had an encounter with a witch as a child that ended in her losing a thumb. What exactly happened to it is unknown.
In The Witchlands, when Cam's brother tries to get him to join his gang, he cuts off one of his fingers.
