The Light Side resolution to Ajunta Pall is exceedingly poignant. Here is one of the biggest, baddest original Sith Lords, whose ghost is wracked by guilt and torment, and you convince him his master will welcome him back if he chooses to return to the light.
Ajunta Pall: If if I could return. Oh, my Master it has been so long and I regret so much (vanishes, having chosen the Light Side)
It might seem Disney-ish to the extreme, but if you play a Light Side male character (or even a Light Side female with mods), and that you romanced Bastila, you save her from the Dark Side literally with the power of love: she's there begging you to kill her to end her torment, and you just tell her that you believe in her, that you love her, and that since you were the Dark Lord, she can also be redeemed. And it works.
The redemption of Yuthura Ban. Particularly since you do it with basically just one Armour-Piercing Question - If Yuthura embraced the Dark Side to save the slaves, when she becomes all-powerful and not limited by things like tenderness and mercy, why would she still care about the slaves?
The beginning of the action on Taris, when Carth reveals that he's not only gotten you to safety but has been watching over you for days. Not so obvious at first, but once you know more about him, you discover you've landed in the safe hands of a seriously Nice Guy
Trask gives his life to save you before the prologue has ended. If you play the Smuggler character in The Old Republic, you find out that Trask came from Alderanian nobility and is remembered as a great hero for sacrificing his life to let Revan escape.
If you play Light side and female, the brig on the Leviathan, oddly enough. After he's singled out for "special attention" from his former commanding officer and mentor in the torture chamber as a means to break you down, Carth "I will never trust anyone ever again" Onasi says "I know you would never intentionally hurt me," and admits that, were your roles switched, he probably would've caved under interrogation to avoid making you suffer.
After The Reveal, your party has a pow-wow on the ship. Carth is in full blown Justifiedparanoia mode. But the rest of the crew? Nope. Starting with Mission, every single member of the crew stands up and announces they still trust you.note Well, HK-47 is programmed to be loyal, and Canderous just admires the Jedi who smacked his people into submission. You can still destroy their trust, but...
Juhani's lines were Dummied Out for that scene, but talk to her afterward, and she is all choked up. Turns out you were the one who indirectly saved her life as a young girl, and later saved her life in the grove. She is humbled and awestruck by this. If you are Light Side, she is elated that you are once again the paragon she seeks to live up to. If you are Dark Sided, it turns into a borderline Tear Jerker as she resolves to help you back.
The "no going back" point on the temple-top, Jolee and Juhani show up and insist on helping you so you do not face what's in there alone. It's doubly heartwarming if you pick the Light Side option, since that means that Juhani has finally paid your character back for saving her twice. It's additionally sweet if you are playing Light Side female and manage to trigger the romance dialogue.
If you get past the claws and the anger management issues, Juhani is an absolute sweetheart, relieved to see an LS player be everything she hoped a Jedi would be, consoling a neutral player with how difficult their decisions must be, or trying her best to try and encourage a DS player back to the Light.
If you run into Dead-Eye Duncan again on Manaannote Cut content, only playable with mods, you can gift him your old duel-ring moniker of "The Mysterious Stranger" to let him quit the biz and finally receive some respect. (Since there's almost nobody left from Taris who can correct him.) The poor guy kinda deserves the break.
The good ending of the Feuding Families quest. If their fathers are still at each other's throats, Shen and Rahasia are still able to be together in the safety of the Jedi Enclave, and that's all that matters to them. Their heartfelt thanks to you is just the icing on the cake. A side order of Heartwarming in Hindsight comes up if you have Carth in your party. He gives his blessing, hoping that the young couple "knows the happiness I once did."
Even better: a successful Persuade check gets you the really good ending, in which the parents agree to settle their feud once and for all and build a new house for the couple.
Game Mod example: In the Brotherhood of Shadow mod, Koybayashi's plea to "Sera Degana" to awake from her Angst Coma.
Also, Solomon's Heroic Sacrifice giving his life to heal Koybayashi, and finally making peace with his lost padawan, his Echani ethos, and the Force itself.
During the final confrontation on the Star Forge, a redeemed Revan asks for Malak's forgiveness and tells him he is sorry for setting him on the path to the Dark Side. Malak's response is that it was his fault for choosing to walk that path.
The end of Jolee's speech after The Reveal. Especially how sincere he sounds. "Does this change anything? I'm not here to judge you. You just do what you have to do. And I'll help if I can".
The cut female-only ending for the first game, if Revan was Dark Side. Basically, Carth would walk onto the Star Forge, alone and unarmed, and make a truly touching Anguished Declaration of Love to Revan, much like what is in the game. However, in this ending, it works—she decides to take her Last-Second Chance, strikes down Bastila, and dies with Carth to let the Star Forge be destroyed, all because of her love for him. And the epilogue? It says that, in millennia to come, they "were not remembered for their crimes nor their weaknesses, but for their deeds, as heroes who saved the galaxy." And the best part is, it's very easy to mod back into your game.
After you control one of your party member and free everyone from prison, Carth, despite his paranoia, give his congratulations to the rescuer. Even to Canderous, despite his dislike of him.
Reconciling Bastila and her mother Helena. They stop arguing and Bastila may have shown care and concern for her mother for the first time in many years. Likewise, Helena put her abrasiveness aside for once and let Bastila keep her father's holocron.
Darth Malak, of all people. Saul informs him that Calo has been killed during a cutscene. He's kneeling in a manner as if he's expecting to be killed. Malak reminds him that while the penalty for failure is death, Saul had nothing to do with it. Coming from someone who previously had an entire planet bombed, that's quite a Pet the Dog moment.
In the Light Side path, if you've completed Canderous's quests, he tells you right after you land on the Star Forge.
Canderous: This looks like the end of our partnership. The battle we fight here will change the face of the galaxy. You are the single greatest warrior of this age, and any battle we fight will bring me honor. I'll stay by your side through anything. I don't think I'm ready to give up this life of mine, this life of fighting, not yet. We have things we need to do here. I'm your man until the end, whatever path you take.