Sooo much in Majora's Mask. Keep in mind that the whole game is played out through the same constantly repeating 3 days which end with the Moon crushing the earth.
*Possible spoilers*
Saving Romani from the aliens.
Cremia's "gift" to Link.
Making Grog's chickens grow, followed by him claiming he has "no regrets now"
Calming the Goron Baby's crying.
Healing Darmani and Mikau's souls.
Igos Du Ikana's speech about friendship.
Putting Skull Keeta to rest.
Reuniting the sea horses.
Playing Ballad of the Wind Fish and making Gorman cry.
Healing Pamela's Gibdo father, followed by her tearfully hugging him and claiming that he's been suffering from a bad dream.
Reuniting Anju and Kafei. I'm not going to elaborate. You have to see this yourself. Claim yourself as manly as you want to be. You. Will. CRY.
Healing Sharp with the Song of Storms, followed by him begging his brother for forgiveness.
And last, but certainly not least, stopping the Moon from destroying Termina. Even if you save the four regions and do all the sidequests, the moon is still going to come down, you either restart time or climb the Clock Tower, and when you do summon all the giants, stop the moon, and kill Majora, the moon explodes into a rainbow. You then realize all of this has stemmed from Skull Kid's increasing feelings of abandonment from the giants leaving him. The whole thing is beautifully summed up with Skull Kid asking Link "will you be my friend?" followed by a montage of all the people you've helped throughout the game.