Heartwarming: My Little Pony: The Mentally Advanced Series
At the end of Bubbles Rainbow Dash lets Derpy stay with the bubbles after she gets the cutie mark. It made this troper go D'aw. Not to mention when she takes her out to the parade.
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.
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.