Fluttershy! Before the Smile Song cemented Pinkie as my favorite character, Fluttershy held that spot. She's just so cute. I have a soft spot for shy girl characters, and Fluttershy is one of the best because her shyness isn't her only defining characteristic. Watching her caring for her friends, and getting angry when those friends are threatened, is always a joy to watch. I also think hers is the best singing voice out of the mane cast.