Chapter 3, the flashback where Lelouch recruits Shirley. the poor girl has a case of Driven to Suicide and throws herself off a cliff. Lelouch uses his dragonslayer magic to save her and then tells her that her gift is real because she had lost her faith in her ability as a magus.
Chapter 9 where Marianne tells Kallen that she’s home.
Chapter 15 where Marianne calms Cornelia down while she’s having post-victory Heroic B.S.O.D. regarding the death of Estellise.
Chapter 26: The Reveal that Selina is Suzaku’s Missing Mom. She only didn’t tell him because of how differentthey are. She also abandoned him to Genbu because she believed he’d grow up better as a human being under his father than with her. She also believes that while she’s made many mistakes in her life that Suzaku was the only thing she ever did right.
Chapter 27: All of the flashbacks to Lelouch and Erza’s past history are this
Chapter 31: When Kallen starts to angst about Kraken’s Eye since it was the first guild she was ever in, it's natural to think that we’re about to get a repeat of her treatment by Iron Star. However, not only are both Kasumi and Kalina genuinely happy to see her and hear that she’s doing well, but Kasumi even apologizes for kicking her out. The guild has a much firmer grip on wanton destruction and policy violation so to find out that they did want Kallen to stay and are glad she finally found a good fit brings a smile to your face as much as it does Kallen’s. What really sells it is Kasumi giving her a big "welcome back" hug.
It gets upped in the Journey to Hell arc when Kasumi and Kalina are more than willing to help Kallen find Naoto
Chapter 35: Mirajane tells Kallen she can always rely on her as an older sister, reminding Kallen of Naoto, but also, possibly filling a void in Mirajane's heart regarding Lisanna, considering when the scene takes place in continuity.
Chapter 39: Elfman and Mirajane's heart to heart moment regarding Mirajane being asked to go on the dangerous assignment.
Chapter 41: For NaLu shippers, seeing Natsu break through the floor to punch the ever loving afterlife out of a wraith because it gave Lucy a Jump Scare can only be seen as heartwarming Ship Tease.
We get more of this in chapter 42 with Natsu giving Lucy a hug telling her he won't let her become a werwolf.
Erza and Lelouch's friendship anniversary celebration is this if you're on board with the pairing.
Naoto telling Kallen that he's proud of her.
Erza saying that Lelouch is what Jellal could have been if he had stayed in her life.
Lelouch treating Oracion Seis, if you don't think it's dumb or out of character, as if they're human to the point that he convinces Angel to surrender and she begs him to help her and her friends.
Chapter 60: Kinana would rather be arrested along with Cobra than live free. It's both a Tear Jerker and a heartwarming moment and a bit funny when you picture Cobra crying like a bitch at how touched he is by how important he is to her.
Later that chapter, how Lelouch encourages Erza that she'll manage to get through Jellal being sent to prison for twelve years is really sweet.
If you're a Natsu/Lisanna shipper, then their reunion scene in chapters 61—where Natsu doesn't realize the Edolas Lisanna is his Lisanna—and 62—where Lisanna up and admits that it's her—is this.
More of this in chapter 65 where they fall asleep next to each other.
Also in chapter 65 is Lelouch finally admitting that he's in love with Erza, though only to himself.
There's also the cute moment of Anya, Gino and Wendy cuddling together.
Suzaku's proposal to Euphie.
Possibly not so much now given recentevents, but hey it was when it happened.
Sorano "Angel" Aguira meets her idol, Marianne in prison
There's also Shirley's and Cornelia's heart-to-hearts with Lelouch.
Every interaction with Lelouch and Erza in chapter 76 is this or a bonafide Tear Jerker
Cana wins cake from Sindel as a wager for a friendly spar. Erza sees the latter crying over it and immediately demands Cana give back the wagered dessert and then caresses Sindel's head, giving her back the cake. Sindel lights up like a 1000 watt bulb. It's so damn cute it could give you diabetes.
Chapter 92 has Erza and Lelouch run into each other by chance and the ensuing scene will make any shipper Squee! like a little school child. Or get diabetes. That's also possible.
A minor one in chapter 95. If you've found yourself particularly attached to EmmaJaeger and TetsuoKogami, then Tetsuo proposing to Emma is this.
After the battle with Hades, Makarov counts the unexpected intrusion of Grimoire Heart as part of the Tenrou Island exam and grants not only Gray, but also Natsu an S-class license, something the latter wanted so much so that he could meet Igneel. It's especially precious given a scene like this doesn't exist in canon.
Also something of a Tear Jerker, but we actually get to see Kagura's reaction to finding out about Simon's death and then she's immediately given a hug by Millianna. Unfortunately, Kagura ruins the feels right afterwards by not taking Millianna up on her offer of friendship.
When we eventually find out Carine's history of why she's attached to Guinevere, it suddenly all makes sense, especially since at the end of that same chapter Carine goes through a bit of Character Development and decides to stop her Clingy Jealous Girl behavior.
There is a flashback in chapter 139 where Jellal is shown giving Erza his meal portion because he knows he might vomit if he tried to force it down. Erza is still hungry so he tells her to eat his portion.
If you support the pairing then 146 has Jellal and Kagura getting together.
After over 100 chapters of building it up Lelouch and Erza finally get together.
Shimon beating the shit out of Philosopher's Stone for the sake of his new girlfriend Chelia.
Kagura and Erza becoming friends at the end of their fight in the Grand Magic Games
Alice and Natsu in chapter 182 as Alice recalls memories from Natsu's infancy that she spent with him while she holds Natsu in Marshmallow Hell is not only this, but also a bit of a Tear Jerker.
Future Natsu's reunion with Erza in chapter 193 given the former hasn't seen the latter in five years because she's dead in his timeline.
Minerva's hug with Mace after the defeat of Mordred is a great way to showcase her Character Development from Alpha Bitch to Sabertooth's trusty second-in-command.
The subplot with Undine and her dead fiance's brother wraps up a subplot in one scene that might've had readers walking on eggshells for over 80 chapters and gives Undine some real peace at heart, knowing that her fiance's family doesn't blame her for his death.
Pick any scene with Lelouch and Erza in the Cracked Gemstone arc. It's guaranteed to have at least one of these.
Whilst still a villain and demon, some of END's action and statements showcase some of the loveable idiot he is in the canon series. END turns down the advance of Enna Elsa without hesitation or thought on account of being Happily Married for what is implied to be centuries. He also shows some Papa Wolf tendencies by refusing to send one of his daughters, Luster, on a mission which might cause her to lose her life. Guess he isn't the complete demon END is hinted to be in the main series.
Chapter 219 shows us that, even if Sorano and Yukino fight, they still love each other. Sorano would go to just about any length to do what she feels is best for Yukino.
And in chapter 227 after a heart breaking moment between the Aguira sisters, not only Chandra is understanding of Yukino's reason to quit fighting, she offers to escort Yukino and an unconscious Sorano out of the battlefield. Its no wonder Yukino is referred as "The Heart of Sabertooth".
Chapter 237: Nunnally comes back to Knightmare Frame complete with a big hug from Lelouch. After everything the characters went through in the last couple of arcs, good news like this is needed.
Chapter 238's ending. AyameFutaba ends up in Knightmare Frame nervous and scared because of what happened to her previous guild, but Knightmare Frame reassures her that she's welcome in their home. Couple this with Kallen acting as her mentor complete with flashbacks from chapterone and you have a recipe for a warm and fuzzy feeling in your heart.