Tubby Wubby Pony Waifu. A surprisingly sweet love song, especially for one about a magical blue pony and an evil monkey in clown make-up.
Made even more heartwarming when you learn that the two singers started a relationship during its production.
I don't know why, but I find this comment from this video strangely heartwarming: "No RDP cheating! RDP will be made on the basis of love and whatever other emotions we keep using. Gorillas and stuff. Gorillas are emotions. I feel strongly about Gorillas. RDP is not for sale! I will use the voice, though."
"Sinking Ships," a song about not letting life get you down. Especially heartwarming (And a bit tearjerking) considering this is the last Rainbow Dash Presents.
With everything Fluttershy has to go through in this series, Rainbow Dash and Applejack are the only ponies that are nice to her.
Along with Celestia for at least a whole conversation.
Episode 22 is pretty much just a long, mellow conversation between Spike and Twilight where they both display that they care for each other as friends. Twilight essentially says she appreciates Spike's help, and Spike says that his concern about a possible conspiracy surrounding Twilight "keeps him up at night".