The Radix: Brynstone encounters this during his showdown with Erich Metzger. He has Radix, and there are two people who want it. One is holding his daughter hostage, another has his wife. Both try to reason why he should save one, and let the other die.
In the second excerpt of Son of Neptune, "June" (Juno) tells Percy that he can endure suffering and tragedy and maybe save his friends, or live happily under the ocean while the world ends.
Jason and Percy become possessed by ghosts and attack each other. Piper is ordered to decide which one will survive.
Also keeps with the History Repeats theme of the series, as Hercules/Heracles was offered essentially the same choice.
Several characters outright state that Percy’s gonna have to make another one sometime in the future, but likely won't be able to, due to his fatal flaw: loyalty to his friends above all else.
Played with in the short story "The Lady, or the Tiger?" by Frank R. Stockton. A king has a "justice" system where he puts criminals in the arena and makes them choose between two doors, one of which has a beautiful woman behind it and the other a vicious tiger. Normally that would just be a sick game of chance, but the story is about a particular criminal whose offense was having an affair with the princess, who knows which door is which. She comes to watch him in the arena, he looks to her to save him, she gives him a tiny signal telling him which to choose... so the question is, is she giving him up to another woman, or killing him? Further complicated by the fact that she knows which tiger and which woman are behind the doors. The tiger is an especially vicious one, meaning her lover would suffer an excruciating death if she picks the tiger. The woman is one whom the princess believes is the third leg in a Love Triangle with herself and her lover. So the question is, is she giving him up to a romantic rival whom she deeply loathes with all her being, or subjecting him to a horrific demise?
The New Heroes novel "Sakkara" plays this terrifyingly straight, to one of the teenage heroes, with no third choice. In a young adults novel.
In the second book of the Sword of Truth series, The Stone of Tears, Kahlan encounters a man who had just tried to kill her hanging from a ledge, about to fall to his death. She gives him the choice of taking her hand and living the rest of his life as an essentially brainwashed slave, or falling to his death. He chooses the latter.
In the Dresden Files novel "Grave Peril", Harry is faced with one of these. Should he rescue Susan and, in doing so, start a full-on war with the Red Court due to violating Sacred Hospitality? Or, do nothing and also allow the destruction of one of the three Swords of the Cross? Harry weighs the choices and decides to save Susan because he believes he has to do what's right, even though the consequences of his choice ripple onward for many novels.
In the Discworld novel Carpe Jugulum, Granny Weatherwax faces a complicated birth that could either kill the mother or the child; she saves the mother because she is still young and will be able to have children in the future. There is some unrelated but great moral concerns given during her explanation. Granny Weatherwax also refuses to inform the husband about this choice or give him a say, to save him from suffering the same choice.
Mrs. Patternoster, the Slice midwife, posits that the choice should have been up to the husband/father; Granny retorts that he's done nothing to deserve being hurt so badly (reasoning that she is better able to bear the burden of a Sadistic Choice than he is). Meanwhile Death quietly takes the soul of the baby and makes a discreet exit.
Dean Koontz's Velocity revolves around this concept. Throughout the novel, protagonist Billy Wiles is sent notes from an unknown serial killer offering him two choices, both of which will cause the killer to kill someone, the victim being determined by the choice Billy makes. As the book continues, things get worse - the killer will kill the woman no matter what, the only question is whether or not Billy will say "Waste the bitch,": because if he doesn't, the woman will suffer needlessly.
A perfect example is in Pawn in Frankincense, the fourth book in Dorothy Dunnett's Lymond Chronicles. Lymond is forced in a game of Human Chess to choose between two small children, one of whom is his own son and one who is the villain's son, without knowing which is which. He tries every possible Take a Third Option (bribery, self-sacrifice, escape) but the writer doesn't cop out. Lymond chooses the one he believes to be his own son; fans still debate why and whether he was right.
In the last book, he offers to answer all of their questions about VFD, but only if they let him out of prison. They refuse.
In Animorphs novel "The Ellimist Chronicles", Crayak presents the Ellimist with three inhabited planets. Each planet has an enormous asteroid hurtling towards it. One asteroid is laced with explosives such that it will self-destruct before reaching its planet. The Ellimist can only destroy one asteroid (and thus can only save one sentient species). Which does he save? Which world would Crayak have chosen to save in advance? If the Ellimist chooses the mined asteroid, he's wasted his shot and two worlds die. If he chooses correctly...one world dies. Crayak does this to him a lot until the Ellimist finally gets too beaten down to play the game any more. Then he realizes his mistake was playing on Crayak's terms in the first place, and just starts seeding life on every world he can find.
In Under the Yoke, a character suffers flashbacks to a Draka brainwashing technique that was used on him: being given control of the switch that directed current into one of two electric chairs, he being sat in one and his father in the other, so that he could only save his own life by committing patricide.
In Stephen King's short story, Riding the Bullet, the protagonist has to make a decision: either him, or his mother will die soon. He saves himself and chooses his mother. She doesn't die, but he still knows that his choice was to let her die.
In one of the Legend of the Five Rings official stories, Dragon Clan champion Togashi Satsu was captured by the mad monk Kokujin and asked which of his two followers would be sacrificed. Satsu initially offers himself but Kokujin refuses saying he'd kill both of Satsu's followers if he didn't make a choice. Once the choice gets made, Kokujin starts preparing the other guy.
Kurt Vonnegut's short story "All the King's Horses" has U.S. Army Colonel, Bryan Kelly, whose plane has been shot down in the Asiatic mainland. With him are his two sons, his wife, the pilot and co-pilot, and ten enlisted men. The sixteen prisoners are held captive by the Chinese officer Pi Ying, who forces Kelly to play a game of chess â€” using his family and men as the pieces. If he can defeat Pi Ying in the battle of wits, then the sixteen captives are free to go, except there is one catch: every American piece who is captured will be executed immediately. This leads to a moral dilemma for Kelly as he is forced to make decisions with the lives of everyone hanging in balance.
The Devil's Alternative is a novel by Frederick Forsyth in which the president of the United States is forced to do this. This is the Devil's Alternative, sadistic choice.
In the young adult Dark Future novel Smart Rats, the teen protagonist must choose whether to silence his mentally-disturbed little sister, or leave her alive to prattle lies that could get his entire family tortured and executed by the secret police. He takes her swimming, and "fails to hear" her struggling in the water.
Hexwood: At the culmination of his Training from Hell, Mordion is given the choice between killing his final remaining classmate — whom he loved like another self — or allow her to be tortured for a year in a way worse than anything a trained assassin could imagine. He takes the first option. It wasn't a hard choice.
His master then explains to him that he will face this choice every time he is ordered to kill someone: either he kills them immediately, usually as painlessly as he likes, or the master will take this revenge. Thus completing the transformation of a fundamentally gentle man into a remorseless killer.
Chauvelin is notorious for his merciless "either...or" ultimatums in The Scarlet Pimpernel and its sequels. His first target is Marguerite Blakeney, who has to choose between helping Chauvelin arrest and execute the Scarlet Pimpernel (aka her husband) or letting him arrest and behead her brother. Thereafter, Chauvelin usually holds Marguerite as the hostage and gives the choice to Sir Percy Blakeney — for example, in The Elusive Pimpernel, he threatens to kill the breadwinner in every family in Bologne if Sir Percy tries to rescue his wife.
In Mikhail Akhmanov's TheGatesOfTheGalaxy, the Mark Valdez is one of the twelve Arbiters of Justice, whose duties include mediating inter-species disputes. They are trusted as always making the moral and just choice, even if it's not in humanity's favor. Earth has been at war with the Dromi for over 50 years with millions dead on both sides. Humans get a chance to end the war in one fell swoop by taking out the Dromi homeworld. They use a Portal Network to get to the Dromi system without detection and proceed to depopulate one of their worlds before moving on to the homeworld. However, the Dromi figure out what's going on and land all orbital hatcheries on the planet, hoping that the humans won't harm "children". While the fleet officers claim that the Dromi larvae are not children (they're non-sentient), Mark realizes he has no choice but to abort the mission, even if his own daughter has to join the fight. The epilogue states that the war goes on for another century.
It's heavily implied to be a Secret Test of Character for humanity at large by those seeking to make humans the stewards of the galaxy. Humanity passed.
In The Roman Mysteries Nubia has to choice between freeing her brother and her freeing her friend from slavery.
Time Scout: Here's your choice, assassin, you can stay here in downtime London where they'll lop your damaged hands off, or you can come home with us and receive the best of modern care and tell us all about your criminal bosses.
Would You Rather: Over 200 Absolutely Absurd Dilemmas to Ponder by Justin Heimburg capitalizes on this trope.
Sara Douglass's Wayfarer Redemption sextet subverts this trope, in-universe and out. Hero DragonStar has the choice to save Faraday, the woman he loves (who in a previous life died this way) or Katie, a little girl who supposedly holds the key to victory against ultimate evil. He chooses Katie to die (against Faraday's protestations), but Big Bad Qeteb - who'd been itching to slit Katie's throat for the whole novel - discovers almost immediately afterwards that he's played straight into the hands of destiny by doing so and is now thoroughly fucked.
The only people for whom it plays straight are Qeteb and Faraday. Katie has always known exactly what has to happen and why. DragonStar has long since realised that she's not a weapon; she's a sacrifice... and saving her is pointless. It doesn't play straight for the astute reader who realises just before Katie dies that her final emotion (aside from stoic acceptance) is relief.
In Tolkien's The Children of Húrin, Túrin is given the choice by Glaurung the dragon to either save his sort-of Love Interest Finduilas, who has just been dragged off by orcs, or his sister and mother who are currently suffering under the torment of the Easterlings. Túrin chooses his family. It turns out that the whole thing was a lie by Glaurung; Túrin's family were actually safe, having fled the Easterlings a while back, and when Túrin realises this it is too late to save Finduilas, who is murdered by her captors.
In Drew Karpyshyn's Star Wars: The Old Republic: Annihilation, a joint SIS-Jedi-Army operation results in the Republic getting their hands on a Black Cypher, a Sith decoder used to send secure messages between the Sith leadership and their capital ships. This is used as part of the mission to take out the latest Sith superweapon - the destroyer Ascendant Spear, which can singlehandedly destroy entire Republic fleets. While the joint team is preparing to infiltrate the destroyer to sabotage its systems in order to cripple it in preparation for an ambush, the Republic intercepts a message using the Black Cypher indicating a number of attacks on key worlds deep in Republic space. They decide to allow the attacks to take place, secretly dispatching relief ships for after the attacks. Why? Because if even one attack is averted, the Sith will know their messages are being intercepted and will reprogram all their Black Cyphers, and the Ascendant Spear will continue to wreak havoc on the Republic. The protagonist decides to try to avert one such attack without compromising the mission.
Invoked in the Thursday Next series, when in First Among Sequels, Thursday is dropped into the Book World and ends up on a boat where sadistic choices occur non-stop. They have to rescue some shipwreck survivors who are carrying a contagious disease, there's only enough food for half of the passengers, etc. Thursday keeps making choices to stall for time before eventually leaving the boat in a lifeboat, reasoning that the choices occur because she is somewhere in the Oral Tradition, and they'll stop once there is no one to make them. However, in this case Taking A Third Option may result in the actual speaker in the real world suffering an aneurysm (which makes the third option itself a Sadistic Choice).
Opal Koboi gives one to Holly in the fourth book of Artemis Fowl, forcing her to choose between saving Commander Root and Artemis. She then compounds the sadism by offering Holly a false third option. And to add more insult to injury, Opal didn't give Holly enough time to save Artemis even if Holly had left immediately.
One is offered to Lena near the climax of Beautiful Creatures. Choose the Light, and every Dark Caster in the family dies, never to harm anyone ever again — but Macon will die as well, and Lena will never be able to have a physical relationship with Ethan. Choose the Dark, and every Light Caster in the family dies — but Macon will survive, and Lena will be given the means to be together with Ethan physically and emotionally.
A particularly sadistic variant happens in the George R. R. Martin novella The Princess and the Queen. Two men hired to carry out a revenge killing demand that a mother choose which of her two sons will be killed, with one man hinting that if she doesn't choose quickly, the other man will rape her young daughter out of boredom. When she picks the younger of her two sons to die, the knifeman tells the boy his mother wants him dead, then murders the other son instead.
In the Guild Wars 2 prequel novel Edge of Destiny, Logan Thackeray has to choose between staying with his band of adventurers to fight the Elder Dragon Kralkatorrik, or leaving to save Queen Jennah. He chooses the latter — and with his departure, dooms the fight against Kralkatorrik, resulting in the dragon's escape, the death of one of his comrades, and general fallout and bickering in the group for years to come.
In More Than This, the prisoner made Seth choose who (out of him and his brother) was to be taken as hostage.