This is based on opinion. Please don't list it on a work's trope example list.
Tear Jerker / Vorkosigan Saga
The epilogue of Shards of Honor, which deals with medtechs retrieving the bodies of the dead from the Escobar War. One of the bodies the medtech finds is her daughter.
Yes, he thought, the good face pain. But the great - they embrace it.
There's a poignant moment in Barrayar where Cordelia, who's always wanted children, is gleefully anticipating the large number of them she can have now she doesn't have to worry about the 'two child only' law of Beta Colony. After reading this part, it's both heartbreaking and heartwarming that she refuses to have any more children and gives up her dream of a large family, for love of her son (any younger siblings would be a candidate for heir, and thus put Miles' life in jeopardy).
The part in Barrayar when Cordelia nearly dies giving birth to Miles, and Aral admits he hasn't been so scared since he was eleven years old: which was when the old Emperor murdered his mother and brother in front of him.
This part in Barrayar, where Aral and Cordelia confront Vorhalas, who's just tried to murder them with poison gas:
"You missed me, Evon." Vorhalas spat in his face, spittle bloody from his injured mouth. Vorkosigan made no move to wipe it away. "You missed my wife," he went on in a soft slow cadence. "But you got my son. Did you dream of sweet revenge? You have it. Look at her eyes. A man could drown in those sea-grey eyes. I'll be looking at them every day for the rest of my life. So eat vengeance, Evon. Drink it. Fondle it. Wrap it round you in the night watch. It's all yours. I will it all to you. For myself, I've gorged to the gagging point and lost my stomach for it."
On the next page, Evon is indeed forced to confront Cordelia directly.
"It wasn't the result I intended. I meant to kill him. I didn't even know for sure that you shared the same room at night." He was looking everywhere, now, except her face. "I never thought about killing your..."
"Look at me," she croaked, "and say the word out loud."
"Baby," he whispered, and burst into sudden, shocking sobs.
Kareen's senseless death, and Cordelia's Sanity Slippage afterward, burning the Imperial castle with an arc thrower, thinking that there could be no blaze large enough to be a suitable death offering for the dead princess.
Burn, you. Burn for Kareen. Pile a death-offering to match her courage and agony, blazing higher and higher— As they reached the door of the old Emperor's bedchamber, she fired the hallway in the opposite direction for good measure. THAT for what you've done to me, and to my boy— the flames should hold back pursuit for a few minutes. She felt as though her body were floating, light as air. Is this how Bothari feels, when he kills?
Really, most of the plot of Barrayar is potentially tear-jerky. There are so many babies and children in peril. This troper loves the book, but read it for the first time while pregnant with her firstborn son. Not recommended unless you like weeping openly on public transit.
Dr Vaagen's re-telling of Henry's death.
Admiral Lord Vorkosigan vs. General Count Vorkosigan in Barrayar
Aral: My home isn't a place, sir. It's a person. (Beat) People.
To put that line in context, in an argument over whether or not to keep Aral's crippled (and as yet still unborn) son Miles, Aral is so angry with his father that Cordelia realizes it's the first time she's truly seen him in one of infamous rages, and Piotr is in the process of disowning Aral as much as he can; this is Aral's response to Piotr kicking him out of Vorkosigan House. He states how little a physical residence means to him...and reluctantly admits how much his father still does.
After an assassination attempt, when Aral and Koudelka are stunned and can't hear very well, Aral reassures the perturbed Kou that it's only temporary. However, logically, the temporary deafness must recall Aral's traumatic childhood injury after his family's massacre. I can't recall now whether it was explicitly discussed in the text, but it was all I could think about.
The part from The Warrior's Apprentice where Miles says he wants to make his life "an offering fit to lay at my father's feet":
Aral: Clay, boy. Only clay. Not fit to receive so golden a sacrifice.
The death of Sergeant Bothari and the final remembering at the end of the book.
The ending of two stories from the Borders of Infinity compilation: "The Mountains of Mourning" and "Borders of Infinity".
During "The Mountains of Mourning", Miles must preside over an infanticide case in a backwater area of his family's district; the baby was killed for having a hair-lip. Miles is initially annoyed at having this time taken out of his shore-leave, but gets sucker-punched by the enormity of what's happened during the disinterring of the baby girl's corpse. When her mother burns a funeral offering on her grave...
Miles, caught short, felt in his pockets. "I have no offering on me that will burn," he said apologetically. Harra glanced up, surprised at even the implied offer. "No matter, m'lord." Her little pile of scraps flared briefly and went out, like her infant Raina's life. But it does matter, thought Miles. Peace to you, small lady, after our rude invasions. I will give you a better sacrifice, I swear by my word as Vorkosigan. And the smoke of that burning will rise and be seen from one end of these mountains to the other.
The murderer in "The Mountains of Mourning" is a thoroughly unpleasant old woman. But while interrogated under fast-penta, she bursts into tears at one point, saying to Miles, "Damn you! What use is your justice to me now? I needed it then ... where were you then?" The implication that back when this nasty harridan was a young mother, she, too, would've been overjoyed to be told she didn't have to kill three of her babies....
The parts of Mirror Dance where Miles' family and friends are mourning his death, at the same time as they are welcoming Mark to the family. The scene where Mark sees Ivan crying breaks this troper's heart every time.
Then there's this subtly sad exchange between Mark and Cordelia, which shows how much she really gave up coming to Barrayar.
“I’ve never heard you analyze yourself, ma’am,” he said sourly. Yes, who shaved the barber? “Me?” She smiled bleakly. “I’m a fool, boy.” She evaded the question. Or did she? “A fool for love?” he said lightly, in an effort to escape the sudden awkwardness his question had created. “And other things.” Her eyes were wintry.
The Turn in Your Badge scene in Memory, as well as Miles and Ivan's first visit to Simon in the medical ward.
Just to twist the knife, Miles later finds that up until he lied to him, Simon wanted him to be his successor. This turns out to be what drove the saboteur in the first place, when he realized that Miles would be getting the job he wanted.
Rosso Gupta's pained, tearful story of the fate of his former crewmembers in Diplomatic Immunity.
Taura's offscreen death of old age at thirty in Cryoburn, even if she died as dignified as she could.
The last three words of Cryoburn (minus the epilogues): "Count Vorkosigan, sir?"
And bear in mind that this is one of Miles' worst case scenarios - that he would not be there for his father's death. "He dreaded the day that some stiff faced messenger would begin by addressing him as "Count Vorkosigan, sir?"" And then along comes Colonel Edwin Vorventa... Excuse me, I gotta go compose myself.
And from the epilogue to Cryoburn, when people object to Emperor Gregor being a pallbearer for Aral's casket, his response is, "The man has carried me since I was five years old. It's my turn."
Even though he gets better, Mile's last thoughts before getting killed are "Wait, I haven't...", which is heartbreaking when you consider his Back Story.
Ivan's birthday in Captain Vorpatril's Alliance. Thirty-five years of starting off every birthday burning an offering for his father in the middle of a Vorbarr Sultana street. Not just a tear-jerker for him, either - his mother got to relive the horror of her husband's death, her son's traumatic birth, and her narrow escape every year for thirty-five years...
Of particular note: a smell she especially remembers from her husband's death (by nerve disruptor hit to the head) is the smell of burning hair. One of the things traditionally burnt in the offering is clippings of the hair of the attendees, which would certainly trigger unpleasant memories. Every. Single. Year.
She also says it's her last time - and it's strongly implied that it's because Tej is with Ivan at the time. Party because she sees they're in love with each other, and she wants to tell the story for their benefit, and also because she's hinting that the tradition can be carried on by Ivan if he wants to.
Also from Captain Vorpatril's Alliance, Lady ghem Estif’s story about her stepson, who went back into Vorkosigan Vashnoi to find his Barrayaran lover, and ended up being nuked along with his boyfriend and the rest of the province. She must have really loved him, because she asks Ivan to pay them tribute the next time he flies over it.
In Barrayar, five-year-old Gregor at his mother's funeral asking Cordelia, "Are they going to kill me, too?" with morbid curiosity.
It is at this point Cordelia realizes she's no longer Betan, but full Barrayaran.
In Cetaganda, Ivan tells a story of how Miles got the two of them buried alive in a tunnel for a few minutes, til Bothari rescued them. Ivan wistfully says that he wishes Bothari were still around to save them. Miles starts to snap then thinks to himself painfully, I miss Bothari, too, and wishes Ivan hadn't made him revisit that wound that hasn't healed (nor has it ever.)