Since there's no Crowning Moments of Nostalgia page, here's one from the Jump Festa trailer:
Mickey: All for one!
Sora, Donald, Goofy, Mickey: And one for all!
In the February trailer, Axel and Roxas have a moment on the clock tower. What really pulls it together is when Roxas says "Got that memorized?" to Axel.
Roxas: You made us a promise. That you'd always be there...to bring us back. Got it memorized?
Also from the trailer Riku telling the Sorcerer's Apprentice!Mickey he's looking forward to seeing them join forces.
A bit more meta than most examples here, but this game is basically Riku's journey to forgive himself for what happened in the first Kingdom Hearts game.
Players can have these moments whenever they pet their Spirits, and then the Spirit responds warmly. For instance, pet your Meow Wow enough, and he'll start licking you.
One of the game's ending scenes. Sora's joyful laughter as he's amassed by happy Dream Eaters.
Joshua from The World Ends With You has several examples which place him here oddly enough, considering his originalcharacterization. Not only did he reveal his wings to Sora and Riku, he recreated the Players after Shibuya was destroyed by darkness.
Sora's reaction to Riku coming to after waking up his sleeping heart? He hugs him. Twice.
Seeing a good chunk of the Organization members, especially Axel, being Back from the Dead and back to normal is nice, especially since, having their memories from before, they aren't all that different as a whole.
Hopefully, the inevitable moment when Lea and Sora meet will be this in spades. We don't even know if it will happen in this game, but someday...
It does happen. At the end of the game, Lea and Sora meet. This would be an "And The Fandom Rejoiced" moment if it wasn't for the circumstances within the plot - the leaked ending isn't that upbeat.
Subverted. The ending isn't quite a happy ending, but it's a lot more upbeat than feared. Basically, Lea pulls a Big Damn Heroes on Sora and the whole group makes it to Yen Sid's tower safely. Not only that, but Sora ultimately fails the exam, but nonetheless he is genuinely happy for Riku, who made it instead. True, now Sora is in Traverse Town, all on his own for the first time, but the Dream Eaters keeping him company and this can drive someone crazy in the long run, but after what he's gone through in The World That Never Was, and considering this is Sora we're talking about, it's not like this is likely to happen. Also, if you saw the last part of the game's opening, you know Sora's gonna be okay anyway.
Rinzler reaching for Sora's hand right before he fell to his death can qualify, even if Sora wasn't able to save him. And it shows that even if this Tron isn't the same as the one Sora knows, he still thinks Sora is a good person and trusts him.
The conclusion to Sora's half of The Grid.
In a call-back to one of Neku's most heartwarming lines in The World Ends With You, when Neku expresses doubt that they'll get back to their own world:
Joshua: But Neku, I thought you couldn't afford to lose. Give up on yourself, and you give up on the world. Neku: Right. So I'll see you there? Joshua: Huh? ...me? Neku: Right. We're friends, aren't we? It's your world, too.
And Joshua's response:
Joshua: *nervously laughs* Maybe it's you that's turning into Sora.
*Joshua walks past him*
Even better. During the ending credits, Joshua gets to join the group, finally solidifying himself as their friend. Seeing Neku, Shiki, Beat, and Rhyme openly accepting him just makes it even more heartwarming. Although, whether or not this actually happens in Traverse Town or Shibuya (or anywhere else) is questionable, it still fits the trope nonetheless.
Riku and Joshua have a rather sweet conversation during the former's second visit to Traverse Town.
Riku: When did Sora get here?
Joshua: Bravo, Riku. Why can't he be this quick on the uptake?
In Kingdom Hearts 3D, Riku sees some of Pete's goons set up cardboard images of Mickey, Donald, and Goofy. He then notes with a smile that those three are always together, no matter what.
Slightly funny, but still heartwarming, in the English dub:
Riku: Yeesh, those three are together even when they're made out of wood.
A beautiful moment in the game would have to be when Sora and Riku use the power of sound to break the spell on Mickey, which is poignant enough, but it is made even better by what plays when they use it. What song does it play? None other than Dearly Beloved.
Not only that, but Dearly Beloved also plays during Riku's speech before he dives back into Sora's heart at the end of the game.
Mickey: Riku and Sora. The Sound Ideas you set free joined together. And when they did, they made a great and powerful harmony.
Mickey: Its like each of you is holding on to a little part of the other.
Sora and Riku's joint Reality Shift, which is a merged rainbow-colored Keyblade... with a heart at the tip of the blade and a paopu fruit◊ as the handle's charm.
In Symphony of Sorcery (Fantasia Land) after Riku offers to help Mickey with the enchanted music, Mickey says that he has a feeling the he and Riku are going to be good friends, making Riku smile. Keep in mind that although Riku smirks a lot, he rarely gives real smiles.
The fact that Satan himself isn't dark enough to plunge his world into Darkness. Symphony of Sorcery has fallen into Darkness and sleep, but Satan himself is apparently not responsible; he doesn't use darkness or anything evil - he just uses his own forces to fight. Nothing that could damage his world is involved, so he is not responsible for it falling to Darkness.
This beautiful little moment.
Mickey: If it's all right with you, can I go help Sora and Riku out?
Yen Sid: How? You cannot enter the world of a dream. Where will you go?
Mickey: Follow the hearts, and you'll find the way. That's something Master Aqua told me once.
When Sora is wandering through the dream version of The World That Never Was, he meets Roxas.
Roxas: This could have been the other way around. But it really has to be you. Sora: Huh? Roxas: There are so many hearts connected to yours. You're me, so you can feel what I felt. Sora: No. Roxas, you're you. We're not the same. That's what I wanted to tell you. That you deserve, just as much as I do, to be your own person. Roxas: *taken aback, smiles* Sora, see? That's why it has to be you.
To put it bluntly, Roxas basically admits that Sora is not just a "good other"; he is a better person than he is, and the only one who can lead both of them from their suffering.
The most poignant thing? Roxas spent his last days being told that he was Sora, his existence a mistake and his "death" the best thing for everyone. Sora is the only person in the series to ever say the above aloud, and one of only a few to even believe it.
For those who want to watch this heart melting scene, it starts at about 9:10 here.
In Soras trip through the dream version of The World That Never Was he runs into Roxas who shares his memories with Sora, including memories of Xion. And during the ending level, Riku is asked questions by Roxas, Ventus, and Xion. Looks like Xion wasnt forgotten after all!
Ventus saves Sora after Young Xehanort shatters Sora's heart, forcing him to become comatose. Ven lends Sora his keyblade armor, shielding Sora the same way Sora was shielding him.
Right before Riku is about to enter the Organization's base and save Sora, he wonders how he's going to get there, than he see's a Meow Wow on the other side of the chasm and a Komory Bat on his shoulder, that are happy to help him. Him petting the bat only makes this scene more adorable. Also serves as a bit of a Funny Moment due to the abrupt music change.
Donald and Goofy watch Riku, and their best friends, Sora and Mickey, go to fight the bad guys and decide that, no, they're not staying behind this time - and steal the star shard to join the fight themselves. They help... by booping the guardian on the head.
Mickey volunteering to wake Sora. His decision isn't just about saving Sora, it's about protecting Riku too. Diving into Sora's sleep is actually fairly dangerous (Mickey talks about the various dangers with Yen Sid) and even though Yen Sid says that Riku has a better chance of success, Mickey's still reluctant to let Riku do it and would rather go himself. That's right, even though there is actually a better chance of Riku succeeding (and getting back safely), Mickey would rather do the dangerous task himself to keep Riku safe.
When Mickey announces that he's going to save Sora, Yen Sid rejects this, but he does say that Mickey would "probably succeed"; he's rejecting Mickey's idea because he doesn't want to lose Mickey.
Riku: Mickey... I really appreciate it. But... I'll go wake Sora up. Look at his face. Sleeping like nothing's wrong- like there's nothing to even worry about. He's always been like that. The three of us would agree to work on the raft, and then this guy would go take a nap on the beach. You see, it's my job to keep him on his toes. Besides, what kind of Keyblade Master sleeps through his test? I'm doing it for me, too. Sora saved me once. And... I heard him call my name. He needs me. Guys, thank you. Sora and I will be back soon.
Doubles as funny. Just before Riku enters Sora's heart to save him, Lea tells Riku that he will help out should the darkness overtake Riku again because "Dark Rescue" is his middle name.
When the digitized version of Ansem the Wise asks Riku what his name is and Riku answers, "Riku," before leaving. This is a Call-Back to Kingdom Hearts II when Ansem the Wise as Diz asks Riku when he was 'Ansem' what his name was and he answered Ansem. It shows how much Riku has changed his opinion about himself since this adventure.
Also, Ansem The Wise and Riku sharing a joke about Sora falling asleep again. It's very low key, but considering Ansem's life thus far, he probably hasn't laughed at anything like that in a long time.
Also, in perhaps his most heartwarming moment in the conversation, Ansem admits that yes, anything is capable of growing a heart. This is a far cry from his attitude toward Nobodies as DiZ (a.k.a. Darkness in Zero), showing just how much he has grown.
When Sora wakes up, the first thing he, Donald and Goofy do is not go off on another adventure. They just sit down together, eat cake and drink tea. Just like actual friends do. They just, for one moment, relax.
Yen Sid proves that he's the better master than Eraqus. Yeah, Riku has done some bad things and dabbled too much with Darkness on occasions... but he's learned how to control it and is worthy of being a Keyblade Master - Yen Sid doesn't write Riku off because of the Darkness, like Eraqus does to Terra.
After Riku earns the Mark Of Mastery and Sora does not, instead of becoming upset or depressed Sora immediately congratulates Riku and tells him that he's happy for him- all while throwing his arm around Riku's shoulder to give him a sort of half-hug. It shows that despite what's happened in the first two games, Sora and Riku are still best friends.
When Sora leaves to go back into the Dream Worlds, Donald is the one who asks him if he's going to be alright, showing just how much their relationship has changed over time.
Seeing the currently comatose and heartbroken (literally) Ventus flash a small smile at the end of the game.
The credits drop letters that spell out THIS LEADS TO KINGDOM HEARTS, and from those words it feels like everything is going to be alright soon.