A bit more violent than your typical Crowning Moment of Heartwarming, but when Honor's lover had been killed, her friends in the Manticoran Navy — including an Admiral, of all people, Admiral Mark Sarnow, Honor's CO at Hancock, who instigates the whole thing — conceive and perform an op disguised as a training exercise for the sole purpose of tracking down the killer. This move was highly illegal and would have cost everyone involved their careers if found out. They did it anyway.
Flag in Exile
Pretty much every single time with Graysons and Honor, but especially in Flag in Exile when Harrington steaders take down Father Marchant and later, the sermon Reverend Hanks gave in Harrington Cathedral.
Andrew LaFollet's first conversation with Tomas Ramirez.
Honor Among Enemies
Honor giving her approval to a naval rating choosing to exercise with marines, with all the subtext it includes.
The PNS Vaubon, commanded by Citizen Commander Caslet, does some truly epic and heartwarming stuff.
Totally annihilate a brutal pirate ship and rescue the two Manticoran MauveShirts that appear at the beginning of the book.
Attack three more pirate ships in order to save a Manticoran merchant vessel from them. When it turns out that the merchant vessel is Honor's Q-ship, she captures the Vaubon, but also extends her personal thanks and congratulations to its crew. Awwwww. And at the very end of the book she gives them a cover story to explain why they did it.
In Enemy Hands
The first reunion between Honor and Andrew LaFollet, when she hugs him for the first time in the series, is beautiful:
...she stumbled forward as he freed one hand from the gun and held it out to her. Her working eye misted, making it hard to see, but his hand was warm and firm as it closed on her too-thin fingers. He squeezed hard, and Honor dragged in a deep, shuddery breath and put her arms around him, hugging him fiercely.
But the second is, quite simply, incandescent.
"He did [save your life], My Lady," another voice said, and Honor gasped. She tried to sit up, but her right hand still held Montoya's, and she hissed in sudden pain as she tried to rise on the left hand she no longer had and the bandaged stump pressed into the firm softness on which she lay. Montoya started to stand, his face distressed, but someone else's arms reached out to support her. Nimitz spilled from her chest, lying beside her, and she pulled her right hand from Montoya's. Her arm went out, and the pain still rippling through her meant nothing at all as she hugged Andrew LaFollet with all the fierce strength in her wasted frame.
Echoes of Honor
The final line of the novel:
Honor Harrington: "We're home, System Command. It took us awhile, but we're home."
Ashes of Victory
Honor's return from being believed dead for two years is a string of heartwarming moments one after another.
Her reunion with Protector Benjamin, who gives the metaphorical finger to a thousand years of Grayson protocol and greets Honor with nothing short of a bear hug and tears of joy.
"Merry Christmas, Wesley."
Her reunion with her parents, and meeting her new siblings, after being 'unavailable' for the last two books, is made especially effective by Honor's words when she first sees them. Nearly all of David Weber's dialogue is very formal, with characters very carefully enunciating and bordering on purple prose at times, even when the characters are explicitly being casual with one another. When Honor finally sees her parents, all of that goes right out the window, and she can only say, "Momma...? Daddy...?"
At All Costs
Howard Clinkscale's funeral and the aftermath, when Honor creates the legal equivalent of blood bonds between her family and the Clinkscales family.
The epilogue: the story David and the Phoenix being read by Honor to her young siblings and her own child. The story is not only beautiful, but a ready made allusion to the state of the empire.
David and the Phoenix is a real book, as it happens.
Nearly every interaction Honor has with Hamish and Emily Alexander after they finally get together, but one that stands out is the birth of Honor's son.
Honor explaining her choice of her son's armsman. Her choice gets vindicated in Mission of Honor during the Oyster Bay terrorist attack, in what serves as a Dying Moment of Awesome for Andrew LaFollet.
Mission of Honor
Eloise Pritchart and Elizabeth Winton thrashing out twelve books' worth of issues between the Republic and the Star Kingdom, then committing to a military alliance. Twenty years and a dozen novels had been leading up to that moment, and to see the payoff, after all the heartache both sides have been through, was astoundingly beautiful.
A Rising Thunder
Thomas Theisman firmly putting a stop to Honor's self-pity party after she's forced to utterly annihilate Filareta's command. He understands her so well, and after so long having to fight someone they each truly respect, to see them working together not just as comrades-in-arms but as friends is unbelievably beautiful.
Combine that with the friendship forming between Elizabeth and Eloise, and it's so desperately obvious that this is a group of people who would, now that they know each other, far rather be fighting beside each other than against each other. Now they finally have the chance.
The Shadow of Saganami
It's one simple line, but the brief mention, as HMS Hercules is getting ready to leave for Monica, that Augustus Khumalo's flag captain Victoria Saunders is surprised to find herself proud of her Admiral. Given how Khumalo had been thought of by every major character up until that point, it's even more poignant.
As a result of the Battle of Monica, the HMS Warlock is placed on the List of Honor meaning that, even after the current Warlock is scrapped, its name and accolades will live on in another ship. The reason this is heartwarming is because Warlock was Pavel Young's ship up until he was discharged and, until that point, its reputation had been stained by its former captain's actions.
Storm from the Shadows
Michelle Henke's reverent reflection on Raoul Alexander-Harrington's birth (in At All Costs), and what it felt like to share that moment with her best friend.
Aivars Terekhov getting the Parliamentary Medal of Valor for the Battle of Monica. Just... that whole chapter. But especially Baroness Medusa's speech — and the way she gently touches his cheek.
Terekhov was much taller than she was, and she rose on tiptoe as he bowed to her so that she could slip the ribbon around his neck and adjust its fall. She positioned the gleaming medal carefully, then looked up at him and—in a gesture Helen was certain hadn't been formally choreographed—touched him very gently on the cheek.
Shadow of Freedom
Estelle Matsuko thinking to herself that while once upon a time Augustus Khumalo was not her favorite person, "those days were gone." Those two have come a long, long way, and it is frankly melt-worthy.
Cauldron of Ghosts
Just before Anton leaves Mesa to go get help, he and Victor are able, for the first time, to say just how very much they mean to each other. This is a Tear Jerker as well because, at that moment, the overwhelming odds are that they'll never see one another again.
Short Story Collections
The end of I Will Build My House of Steel has Queen Elizabeth being woken up by Sir Thomas Caparelli to inform her of Admiral White Haven's victory at Barnett. He opines that the Star Kingdom will be in a position to dictate terms to Haven in the next four to six months.She thanks him levelly, and allows him to return to work. Then, in the middle of the night, alone but for her treecat Ariel, the Queen of Manticore descends to her family crypt to visit her father's grave. She reflects on the sacrifices made and traces her fingers over his epitaph, letting her tears finally fall free.
From "The Service of the Sword", Captain Michael Oversteegen's speech to soon-to-be-Ensign Abigail Hearns:
The entirety of the relationship between Eloise Pritchart and Javier Giscard. The series has surprisingly few prominent romances, and this one in particular is a shining example of two people finding love in darkness and using it to accomplish an extraordinary end.