The very first is Ryu's sacrifice to protect White Base, even when he's badly injured. Though, in the TV series version, the aftermath is maybe a bit overdone with the whole crew standing at the end, all blaming themselves.
Garma Zabi's death in episode "Garma's Fate" was really tragic, and Icelina's useless Roaring Rampage of Revenge wasn't much better.
Michelle Ratockie's death. And even more, her ghost telling Kai Shiden that, as much as she wanted to help the White Base, she also wanted to be with him, and Kai says it's not fair that she had to die for him anyway. And her siblings... those poor kids! T-T
Who could forget when Lalah dies protecting Char. I mean, everybody saw it coming a mile away when it happened, but my god when it did you felt so bad about it. She was protecting the man who saved her and whom she loved, and Amuro killed the woman he loved. It also add to the rivalry between Amuro and Char, which lasted 14 years and was finally resolved after two more wars in Char'sCounterattack.
Amuro:"I did something I'll never be able to forgive myself for... I killed Lalah! Why? Why did this happen?"
The ending of the original series: after his bittersweet victory over his rival Char, Amuro was losing his will to live. Then he finally realized how much his shipmates cared for him; he escaped from the enemy fortress and battle, and found said shipmates, as he tearfully reunited with his adopted family.
For some reason, the destruction of White Base: That ship was their home from the destruction of the first colony. No matter how fierce the battle, whether it was in space or on Earth, and what comrades they lost, they always returned there. To see them floating outside and watch it break into fiery pieces... well.
Four Murasame's death in the episode "Forever Four", remembered as one of the best episodes of the Gundam franchise. In fact, a certain death scene in Gundam SEED Destiny (Stellar's) was basically copied from this very scene.
Another tear jerker for this series is when Kamille kills his "little sister" Rosamia. She was basically mindscrewed by the Titans and only wanted a normal life; Kamille felt bad when he killed her, because he wanted to see her have a normal life in the end.
What really makes it hit home is her last words, "Brother, I've found you.".
The next to Four's death was when Kamille's mother, Hilda, was killed. He was trying to save her and just about did, then Jerid has to shot her capsule exposing her to the vacuum of space without a space suit on. It's a tear jerker because it happened right in front of Kamille, not to mention she may have been a Missing Mom but she still cared for him way more than her Jerk Ass husband.
I think the saddest part of her death was how Kamille lingered in the room with her. You could really see his hesitance in leaving her body there and the way he turned back to her as he opened the door was the saddest thing in all of Zeta Gundam and is perhaps the saddest launch announcement ever.
It's easy to forget in among all the heroic deaths in episode 49, but the death of Jerid Messa is just depressing. To see a character, even a villainous one, who's been with us since the first episode, who we've learned to sympathise with, die such a pointless, meaningless death, is honestly pretty heartbreaking, especially since he wasn't that bad compared to the rest of the Titans.
Not even ZZ is free of tear jerkers, despite its beginnings. Cecilia's Heroic Sacrifice, which her old boyfriend Torres never knew about since Judau, who *did* know, didn't have the heart to tell him? Leina's fiery "death" and Judau's creepyHeroic BSOD after that? Emily's death and the destruction of the La Vie En Rose? Hayato's Heroic Sacrifice? Princess Sarasa's death, which emotionally crushes her boyfriend Mondo? Elpeo Puru's pointless and tragic death trying to protect the only true family she knew? Puru Two's death after her Heel-Face Turn?
Gundam Evolve has retconned Puru Two's death. Too bad everyone else that died in the series, including Sarasa, is gone for good. Plus, the whole thing with Masai's heart-wrenching considering how fighting the Gundams was the only thing she could do to honor her brother's death and after her Gelgoog got destroyed she was left in a catatonic state.
The pilot in Evolve is actually another Puru clone. Considering Gundam Unicorn features a grown-up clone too, and they weren't all shown to be destroyed at the end of ZZ.
Hell, even Glemy's is a little sad, considering it's Roux who kills him.
Roux: I'll never forget that you loved me...
Watching Haman Khan, realising that Judau is right, choose to commit suicide.
This series is packed with the motherload of Gundam Tearjerker moments- the brutal death of Uso's mother, the death of Odelo, even Chronicle's demise as he pleads for his sister to save him.
YMMV on that last one; something about the sudden "thunk" right before the commercial break just made it seem narmy to me.
The most outstanding one of all, though, is the final action of the Reinforce Jr. The ship's just been hit, disabling its left engine. Robert Gomez and the others know that they're not going to get out of their situation alive, but they also know the young members of the crew have to live on- he orders everyone except himself and the remaining old folk to evacuate the ship, and the evacuees can only look on in horror as the Reinforce Jr. advances towards the Zanscare fleet- while two of the old folk commandeer a heavily damaged mobile suit and use it as a turret to defend the ship, no less. The waterworks come, however, when, despite the ship being heavily damaged and everyone else dead, Gomez, with a grin on his face, rams the Motorad squadron as his last act. And if that isn't tear-jerking enough, listen to the song that's playing.
Given her reputation, I may be the only one who feels this way, but honestly, Katejina at the end of the very last episode. Due to her brain damage, she doesn't remember any of the horrible stuff she's done; she's not raging at the main characters or herself for her current state. Thinking of her adorable conversation with toddler Karlmann, she might as well not even be the same person. She's just a lonely, sad girl on her way to a town she doesn't remember isn't there any more.
All of the Shrike Team girls' deaths were very sad, but the kicker is Mahelia's demise, and later funeral. She was such an adorable Cool Big Sis and seemed to understand Usso well, and then... things go like they did.
There are at least two for this movie. The first is is when Hathaway kills Chan for killing Quess when he was trying to save her and had pretty much succeeded. Chan was awesome and her death was sad indeed.
The biggest one is When Amuro died trying to stop Axis from hitting Earth, and the Redshirt Grunts on both sides tried to help. They succeed, but many lives are lost in the process, and Amuro (along with Char) disappeared (the record being that they're both KIA.
I'm definitely in the minority here, but Quess's death hits me pretty hard. She was just a troubled girl from a dysfunctional family who got played like a piano by Char. That alone strikes a pretty personal nerve in me, but to see her story end like makes me feel like getting stabbed in the gut. All the bashing she gets doesn't help it either.
Don't forget about Kayra Su's death. She was being held hostage by Gyunei in an attempt to defeat Amuro in his Nu Gundam after a battle that resulted in her mobile suit being destroyed but her being capture in the escape. Gyunei warned Amuro not to try anything funny, as he was holding Kayra in the palm of his mobile suit hand, but Amuro mistakenly let loose his fin funnels as a diversion to try stop Gyunei. Gyunei clearly sees what Amuro is doing and hurls Kayra's body into space, blaming Amuro for her death. After Amuro kills Gyunei in the resulting fight, he recovers Kayra's body and brings it aboard the Ra Cailum while shouting at Astionage Medoz (the ship's mechanic and Kayra's lover) to not look. WHAT MAKES THE WHOLE SCENE WORSE IS THAT KAYRA WHISPERED TO ASTIONAGE THAT SHE LOVED HIM BEFORE SHE LAUNCHED(he didn't hear her, sadly), AND THEN ASTIONAGE DIES JUST MINUTES AFTER HER BODY IS RETURNED IN AN EXPLOSION OUTSIDE THE HANGER!!!
The scene in Episode 8 of 08th MS Team, during Shiro Amada's proving grounds recon mission which would serve the purpose of proving he was not a traitor. He ended the mission firing a bazooka into a Zaku cockpit, killing the pilot inside, who had previously been established as a conscientious and more-or-less friendly person. Even though both she and Shiro were forced into the situation due to extenuating circumstances, it was the despair on Shiro's face before he fired the bazooka that was the real hit: due to his growing relationship with Aina Sahalin and his understanding that one's side was not related to one's humanity, he had promised himself that he wouldn't kill anyone. In the end, he found himself personally pulling the trigger, betraying the promise he had made, and all to end the life of someone who really didn't deserve it.
The final episode, when Bernie dies trying to save the colony from a nuke that's already been stopped, fighting against his romantic interest Christina without either of them knowing it, and almost manages to win the duel despite being hopelessly outclassed piloting a repaired and poorly armed Zaku against her new Super Prototype Gundam, with his death unfolding right in front of Al, a boy who had looked up to him like a kid brother. Then there's Bernie's last video, and the new school ceremony—the whole of episode 6, in short.
Dorothy, when she shreds her Magnificent Bitch facade and panics after Zechs decides to reject Treize's peace offer and blast his mobile suit. This is the first time that she ever shows raw and real emotions without bothering to restrain them (like when Duke Dermail died and she was shocked for a while, then recovered and used it for a Rousing Speech) and begs him to not do that, going as far as screaming a Big "NO!" and struggling with Zechs while still pleading for Treize's life.
Treize's death. The way he went down with such grace was gut-wrenching.
Trowa being forced to destroy Deathscythe, or else blow his cover. Duo freaking out was bad enough, but Trowa's shock as he notices his own tears floating around him was so sad.
Heero's "World of Cardboard" Speech to Wufei in Endless Waltz. Specially when in a small and soft voice, almost a whisper, he asks Wufei "how many times will I have to kill that girl and her dog again?
Relena's brief Heroic BSOD when her adoptive father is killed.
Also, her reaction when her mom is about to tell her the truth about her heritage as the Princess of the Sanc Kingdom:
Relena: *hugs Mrs. Darlian* "Please, mother, don't say anything! Just... Don't stop being my mother!"
Otto's death. "LONG LIFE KING ZECHS!", indeed.
One from the beginning: the death of a young Oz cadet in Noin's arms, after the bedrooms are bombed by Wufei. "Milady, I'm sorry... I really wanted to go into space...!"
The mangas also have their share of sadness. I.e.: the Heroic Sacrifice of King Peacecraft (which is also a tear jerker in story as his former butler Pagan tells Relena how her biological dad died to save both of them and the man who would adopt her as his own child, Duo's backstory as a whole (specially Sister Helen's death), the passing of Heero's caretaker Odin Lowe Jr., No-name's confrontation with Middie Une, the girl who loves him and yet still betrays their group to help her family., and the death of Wufei's Plucky Girl wife Meiran.
While this series doesn't have too many tearjerker moments, what with the death toll being kept low by Gundam standards, Sochie's fate might be one.
For an actual death, try the King of Adeska, though it may overlap with a Moment Of Awesome.
And Dianna's apology to Kihel and Sochie's father in Episode 10.
Teteth Halleh's death. Although she was a Moonrace spy for Agrippa Maintainer, she did so to save her mother from poverty. She's shot in the head trying to take the gun she used to take Loran and the Turn A Gundam hostage, by accident no less!
The worst part came several episodes later: Several moonrace citizens are released from their stint in cryosleep. One of them is Teteh's mother, asking around futilely for her daughter.
Gavane Goonny's death. When you consider that he was about to marry Sochie the very next day, he goes off on a night-time raid to acquire some newly uncovered Moonrace technology out in the mountains. He and his Borjarnon (Zaku II) team find the tech, but don't realize that the are ACTUAL ARMED NUKES that will detonate at the slightest disruption. After a battle with the Moonrace suits, Loran tells everyone on the area to run away as far as possible, but Gavane was underground and unable to hear Loran's message. Gavane manages to set off one of the nukes by mistake, causing four more to cook off and create the episode's titular 'sunrise at midnight' while the rest of the cast watch in horror... Cue a tearful Sochie in her wedding dress in the following scene.
Both the first and second series of this are filled with these. The first has one at the end of practically every episode, as test pilot after test pilot is lost, their accomplishments being in vain, with Zeon sinking further and further into defeat. The kicker comes in the final episode, wherein, at the end, Oliver, Monica, and the rest of the Oggo recruits seemingly die in a Last Stand against far greater numbered Federation forces. Thankfully, however, simply put, they don't.
Oliver suceeded in making a CMOA out of it, none the less. He made the enemies think he's Char!
MS IGLOO 2, however, has so far dished these up in the same manner with no respite, and it's made worse by just how bad the Federation's situation is, at least in the first two episodes. Barbarry's futile last stand against an unaccounted Zaku and Hermann's out-of-the-blue and ignoble death mere moments after exacting revenge against his nemesis- quite freshly in the wake of the former telling his major that he collected the dog tags of as many fallen comrades as he could to make them live on in his memory, and also in the wake of him lamenting yet again that he was the only one who survived, and in the wake of the latter telling his tank driver that he has neither home nor family to return to- has made this series downright depressing, with some claiming that it's on V Gundam's level in that department.