There are actually quite a few tear jerkers in Warhammer 40K literature - usually small, fleeting moments that remind the reader that the characters are still human beings. This troper vividly recalls an account about Commissar Yarrick during the War of Armageddon. He had just learned that another city had fallen to the Ork invaders, with the defenders being heroically wiped out to the last man. He immediately went to his quarters, and the account goes on to say that "Some say he prayed to the Emperor and renewed his faith. Those who knew him well say he wept." And this was from a badass who once fought a seven-foot beast hand-to-hand with one arm torn off, killed it, and then had its weapon grafted to the stump of his arm.
At the end of the Night Lords novel Blood Reaver, the death of Hound. Who knew that we could feel sorry for the mutant heretic?
This troper got a little misty during The Eisenhorn Trilogy when Aemos died, uttering his trademark "Most... perturbatory...".
Really the entire last half of Hereticus is a tear-jerker. Dan Abnett really is good about making you care about characters.
Oddly enough, Bequin's death didn't seem all that tragic to this troper, even if it was made worse by the gamble that cost her her life not working, but it was Fischig's death that brought tears to his eyes. Right up until the end, he truly believed he was saving Eisenhorn, and almost realized he was mistaken for summoning the Inquisition, but then he's nearly driven mad when the daemonhost shows up and nearly kills Eisenhorn himself.
When reading Storm of Iron this troper was cheering for the Iron Warriors up until they assaulted and breached the fortress in order to steal the Space Marines' gene-seed and began wiping out the defenders. The Imperial Fists desperately trying and failing to hold off the Chaos Marines, and especially the Guardsmen running through the gene-seed vault, desperately trying to destroy all of the gene-seed while being massacred by the Iron Warriors. This line was the last straw: "There was no way they could destroy it all before the Iron Warriors came to kill them. But they would try. It was all they had left."
In Kind of a follow up to this. In the book Dead Sky, Black Sun we meet the tribe of the Unfleshed, a group of mutant cannibals that stalk the wastes looking for meat. It's later that we learn they are the failed attempts of the Iron Warriors to breed more of their kind using the stolen Gene-Seed and they all have the mind of children that still worship and love the Emperor and try to feed and protect the weaker members of the tribe. Ok lets run over that again, the hate spawned children of a HORRIFYING breeding program build a shrine to GOD in HELL, treat each other with care and respect, and ask a stranded Ultra Marine if God still loves them. SCREW Manly Tears I got weepy
Dear lord the line "There should be no more of us" gets me every time.
In the Ciaphas Cain novel Cain's Last Stand, Commissar-Cadet Donal's last stand, alongside Governor Trevallyn, covering Cain and his team's escape from the governor's palace. Made even more powerful by Cain's last words to Donal before leaving, where he takes off his red sash and gives it to Donal, formally christening him as a full-fledged Commissar.
Then, at the end of the book, Donal comes back under Warmaster Varan's mind control. With Jurgen's help, Cain briefly breaks the control over Donal's mind, during which he manages to smile and commit suicide. The real hitter is when Cain walks away, quietly folding up the same red sash.
This event seems to cause him to snap a little. Notably, his actions afterwards are pretty much free of his usual self-deprication and justification.
A similar scene plays out in the novel Grey Knights. Thanks to a conspiracy hatched by a rogue Inquisitor, an Imperial battlefleet was fooled into thinking that the Grey Knights were actually an enemy force. Unwilling to engage his fellow Imperials, Justicar Alaric ordered his ship, the Rubicon, to charge straight for the planet where the Inquisitor was hiding, ignoring all of the damage they were taking from the Imperial ships. It's a suicidal order, but the over one thousand men and women that was the Rubicon's crew did their duty without hesitation. Thanks to their efforts, Alaric and all his Grey Knights made it to the planet, even though the Rubicon and the entire crew perished in the process. Just before they died, Alaric realized that he never really got to know any of the crewmen. He recognized an officer over the radio, and this was their final conversation:
Alaric: Good work officer. What is your name?
Officer:None of us have names. Deployment in six minutes, brother-captain. The Emperor Protects.
Upon landing on the surface, Alaric then proceeds to give the following speech:
We do not know what our chances of survival are, so we fight as if they were zero. We do not know what we are facing, so we fight as if it was the dark gods themselves. No one will remember us now and we may never be buried beneath Titan, so we will build our own memorial here. The Chapter might lose us and the Imperium might never know we existed, but the Enemy - the Enemy will know. The Enemy will remember. We will hurt it so badly that it will never forget us until the stars burn out and the Emperor vanquishes it at the end of time. When Chaos is dying, its last thought will be of us. That is our memorial -carved into the heart of Chaos. We cannot lose, Grey Knights. We have already won.
This troper got some tears flowing after reading Lord of the Night when, in quick succession, Mita and Sahaal were hit by crises of faith, both led to believe that they were both lied to their entire lives and that those they admired and looked to for guidance (The God-Emperor and Konrad Curze, respectively) were Broken Pedestals. In Sahaal's mindscape, after an Eldar traps both of them in there, they confront each other and find that they are kindred spirits.
And then the ending (the real ending, before the sequel hook). Despite everything, "Ave Dominus Nox!".
Similarly, in the novella "Descent", the last use of the line "Nobody hunts like House Ty!".
For this troper, there's the last part of The Last Chancers, where Kage regains control of himself from a Daemon, before he was about to kill Colonel Schaeffer looks at his comrades and himself and has a personal revalation of what it means to be a Last Chancer, then performs a Heroic Sacrifice.
The revelation he comes to right before it really makes me misty eyed.
It all becomes crystal clear in that moment of awakening. Sacrifice, the Imperium is built on it. The sayings are all true. The Blood of Martyrs is the Seed of the Imperium. The Loyal Slave Learns to Love the Lash. Only in Death does Duty End. For ten thousand years we have endured, sometimes we have prospered, other times merely survived. For a hundred centuries we have fought and died, spilt the blood of of our enemies and our own over an uncountable number of battlefields. Mankind has sacrificed itself, for itself, so that it might last another generation, and another, and another. Those sacrifices are for no greater cause than the acts themeselves. It is done in the unspoken hope that some day, perhaps in another ten thousand years, a generation will live without sacrifice and mankind's destiny is assured for eternity. The Emperor will not remember you by your medals and diplomas, but by your scars. It is not only in death that we offer up our lives to Him, but also in life. We are not judged merely by the manner of our deaths, we do not earn His eternal grace merely by dying in His name. It is by the way we live out our lives before we die that defines who we were. it is easy to sacrifice a body, for it's nothing more that a mortal shell for our soul. To sacrifice your life, not your death, is the ultimate test of faith. It is a test I have always failed. I have lied and cheated and killed my fellow men for my own reasons. I have squandered the opportunities for glory I was given. Time and again I stood upon the precipice of true sacrifice and turned away. Von Strab's look of triumph turns to horror as I fling my arms around him, lfting him off the ground. I see von Spenk's astonished face flash past as I drive forwardsm with the overlord in my arms, the panicked bellows of Urkug sounding in my ears. His legs hit them rope barrier and buckle, and my momentum carries us forward, toppling us head or heels into the precipice. Now I truly understand what it means to have a Last Chance. I'm glad I finally took it.
Also, Lorii. Something of an Iron Woobie, gets majorly shafted in all of the books and her part in it all ends in Nausea Fuel.
This troper puts up the last part of Ravenor, where Carl gets taken over by Slyte and continuously begs Ravenor for help until Kara tried to vouch for him. While they were able to avert apocalypse, the team was broken up, much of its members leaving after being emotionally shattered, and Ravenor is on trial for going rogue, with only Patience, Kara and Maud staying with him.
There's also something strangely moving about Molotch's death, even after he spent the novels running around, butting heads with Ravenor, his just giving up after all those chases that cost them a lot and in the end it all seems so small.
Castor gets a speech almost as good as Sturnn's in Retribution.
Castor: Merrick, the life of a Guardsman is to die. It is my job to send them to places where they will die. I am not afraid to spend soldiers, but I never waste them. (Later) So, you can continue with your attempt to kill me, but killing you Merrick would be very... wasteful.
Exterminatus You can tell no one wants to do it. Not even the Marine at the trigger. And just before there's this beautiful picture of Typhon Primaris, lush and green with waterfalls spilling over, and you know what's about to happen and you can't stop it...
From the same series is this. Jonah Orion has been possessed by a greater daemon, with all his will, he fights the beast and forestalls its regeneration of his body; the exchange below begins:
Tarkus: He fights you still.
Daemon: A desperate and foolish gambit. All he can do is forestall my repair of his flesh. By all means, kill this body. It will then be my pleasure to drag the stubborn soul of Jonah Orion into the depths of the Warp.
Tarkus: The Emperor protects the souls of the Faithful. And Jonah Orion has proven himself true.
Daemon: The Emperor? Your 'god' is but a withered corpse on a throne, he cannot protect anyone! Kill me now and nothing will save Jonah Orion!
Tarkus:The man who has nothing can still have faith.
Jonah Orion's fate is utterly nothing compared to Tarkus' if you Corrupt him instead. This troper never thought Chaos Space Marines could actually be the good guys.
Thaddeus: What power could be worth betraying us all?
Any love for the Path of the Eldar series by Gav Thorpe? This troper's only picked up the first book, and found Korlandril's slow but sure descent into Exarch status a bit heartbreaking, given how he was breaking off all ties with everybody he knew and loved... and then had his self worn away by an ancient Exarch spirit. Worse was the end of the book, where Korlandril's gone, Morlaniath (the Exarch) is gone... just... Phoenix Lord Karandras...
The Space Marine Battles Novel Rynn's World has an especially heartwrenching scene that doubles as a Crowning Moment of heartwarming. Captain Cortez saves a Mother and her children (one of whom is just a baby)from being murdered by Orks. Chapter Master Pedro Kantor is less than pleased with this development, as there are (to his knowledge) only a dozen or so Crimson Fists left after the destruction of their monestary, and they cannot afford to bring refugees along. But Kantor says that the family can tag along as long as they can keep pace with the Space Marines, which anyone will tell you is no small feat. After a while, the mother becomes tired and unable to keep up. Kantor moves to the back of the column, to (as the reader is led to believe) "grant her the final mercy." As he kneels next to the mother with his wrist mounted storm bolter pointed disturbingly close to her head, we believe he's going to kill her. Then, after the mother pants that she tried, but her children were just so heavy, Kantor, (who, I feel the need to stress, did not want her there in the first place) replies with the following.
Kantor: You did well to bring them this far....It is time that someone carried you now.
As he picks her up in his arms and carries her the rest of the journey to rejoin their remaining battle brothers. If that doesn't encapsulate what it truly means to be a Space Marine in Warhammer 40k, I don't know what does.
The Space Marines Battles novel Legion of the Damned actually has one. During the battle in the cloister Zachariah Kersch sees his absterge Bethesda being attacked by two Flesh Hounds of Khorne. She is the only person who has been consistently nice to him, even his own servants believed Kersch was worthless after his past failures, but Bethesda always believed in him. He grabs a whip and gets it around her leg in an attempt to save her, even the company Librarian tries to help by blasting the Hounds who are sadly immune to psychic powers. Kersch is not strong enough and the Hounds drag the screaming girl into an alley. You can guess what happened next.
"I wanted to be a hero. You can see how that turned out."
In Eisenhorn, this happens in one instance at the Thracian Gate when a Crowning Moment of Heartwarming get subverted. A space marine cradles an injured child, intending to carry him safety. It turns out the child was one of the captured psykers that got loose in the confusion, and he made old Gregor kill the marine, and very nearly himself if it weren't for Voke's Big Damn Hero moment.
In Void Stalker there are a few Tear Jerker scenes. The best is Talos Valcoran's death. He is the last survivor of 10th company, barring Variel and Lucoryphus, and knows that he is doomed to die from gene-see rejection in a few years and admits that he never hated the Night Lords, he hated what they made him into. He calmly walks towards Jain Zar, the Void Stalker, and allows her to impale him before detonating every grenade he has to take her with him. He succeeded.
Then Cyrion's death. Cyrion is wounded by Jain Zar and dies in Talos's arms. He is blind from the burns and gives his last request to Talos to not have his gene-seed extracted, stating that he just wants to rest, which Talos promises. He then dies with the final line, "I'm dying," he said. "Everyone else is dead. The slaves escaped. So..." he breathed out slowly, "...how are you?" Definitely a tear worthy moment.
Uzas's death is worthy of tears, even more so because of what happens afterwards. Uzas finally realises that he is not responsible for many of the murders he has been accused of, Cyrion is. He attacks Cyrion but before he can kill him Talos fatally wounds him, and tells him he is the worst excuse for a Night Lord in their history and that even Ruven was better than him. But before he dies Cyrion actually apologies to him posthumously, a traitor marine actually apologies to somebody and means it.
Xarl's death is much earlier on but is no less heartbreaking. He dies saving the rest of First Claw from a Genesis Chapter Company Champion. His last act is to tell Talos that he was wrong and that there is no shame in wanting more in life than just survival. He falls to the ground, dead, after finishing his sentence. Talos then carries out his cremation and harvesting himself, and cries after burning his friend's body.
Mercutian has a heartbreaking death as well. He is mortally wounded by Jain Zar during the fight in the catacombs and volunteers to stay behind and buy them a few seconds. He battles Jain Zar ferociously even though he is dying. She impales him and leaves him to die, giving him the chance to shiv her in the thigh. She finishes him off quickly, but the wound he gave her was the reason that Talos and the others had a fighting chance against her.
The novel The Siege of Castellax has a rather surprising Tear Jerker moment. When Over-Captain Vallax escapes the Orks he unwittingly leads a team of Ork Kommandos into the Iron Warriors's citadel and is lambasted by Captain Rhodaan for it. Vallax is horrified by his actions and volunteers to stay behind alone while Rhodaan and his Raptors go off to deal with a traitor in their ranks, despite his armour weighing him down, his weapon being a beaten-up Ork piece of crap and part of his brain is still exposed from the Ork's tortures, and above all that he despises Rhodaan completely and has tried to kill him multiple times, he still stays behind to buy them the time they need, because they are his Legion brothers, and dies fighting. Later on the Ork Kommando Kaptain Grimruk has his head and thinks that Vallax fought exceptionally well.
In the novel Pariah, the main character Bequin finds several ancient toys as part of her mission. The toys are so old that they pre-date even the Horus Heresy. She notices that the toys still have the letters "CCCP" written on them, and she asks what they mean. The store owner simply replies:
No one remembers anymore.
"CCCP", for anyone who doesn't know, stands for "Союз Советских Социалистических Республик", which in English is Soyuz Sovetskikh Sotsialisticheskikh Respublik - Union of Soviet Socialist Republics. In other words, they are the last relics from humanity's first space faring civilisation, and possibly the last remnant of "our" era in the living nightmare that is the 41st millennium. And they will be forgotten or destroyed very soon.
Makari the banna wava. In cannon, he was sat on by Ghazhkull by accident and fed to a squigg without a second of thought. In fanon, however, he was the only being that Ghazhkull had any compasion or sympathy towards. In a battle against humans, Makari got killed, thus fueling Ghazhkulls hatred towards humanity and avenged his favorite gretchin by whiping out the human planet. He still visits his grave from time to time, mourning the death of the single person he had ever truly cared about.
Everyone knew Orks were belched back into another body after they died. Not Gretchin though. No Gretchin could ever replace Makari
Magnus the Red's reaction when he realises exactly what he has done in his attempt to contact the Emperor. Magnus, who is easily the Primarch most concerned about the preservation of knowledge and culture, completely destroys his chambers, smashing dozens of unique and priceless artifacts in his grief. He seems to know that he not only completely messed up the Imperial webway and, by extension, his father's plans, he also has played a significant part in occupying the Emperor and preventing him from acting personally against Horus.