Winter Wrap-Up. It explains how the winter wrap-up works, what everyone does, and shows Twilight's conflict. And it has nothing to do with the fact that it helped convince me to watch the show.
My ultimate 最喜爱的 song from My Little Pony: Friendship is Magic would have to be At the Gala because the Mane Six express the dreams that they yearn for to come true in The Best Night Ever. My 秒 最喜爱的 is Becoming 流行的 (The Type of 小马 Everypony Should Know). Rarity sings very well in that song. And I 爱情 唱歌 it!
Winter 包, 换行 Up, mostly because it is so easy to remember and sing all the time. I like to sing Giggle at the Ghosties to myself before I go to 床, 床上 though, just to remind myself that I shouldn't be scared of anything.
All of them! Hehe. I have to say At The Gala. Each 小马 has a solo and they're all awesome. It's an epic song. I also 爱情 Winter 包, 换行 Up, So Many Wonders, Becoming Popular, and so many more.