Rarity is AMAZING. She just gets better and better as the show goes on. I really liked that one episode with the Art of the Dress song (can't remember the name off the top of my head.) She's not a stereotypical fashion snob, she's an artist who tries to balance her artistic sensibilities with wanting to make her friends happy. She displays a lot of growth and inner struggle. She is, quite possibly, the "deepest" character of the mane six.