Hard to say, here are a few. Haruhi Winry Rockbell Rukia Kuchki Youruichi Major Kusinagi Nami Nico Robin Shuurei Hong As for Why? I just like all the English dub voices of these characters.
So many need a second season I'll list what I can remember. Pumpkin scissors Fruits Basket Kenichi The Mightiest Disciple Ghost Hunt There are more but my memory is failing me at the moment.
This is a very hard choice but if I had to I would say Fullmetal Alchemist: Brotherhood Other contenders: Avatar: The Last Airbender (Yes I Know it's not technically Anime) Ouran Highschool Host Club The Story Of Saiunkoku Bleach One Piece Helsing (TV and OVA) And I am sure there are others I am forgetting.