Avatar: The Last Airbender Characters in Alphabetical Order

In alphabetical order, provide the names of Avatar: The Last Airbender's 20 most significant characters. Granted, "most significant" is a pretty subjective parameter. I'm mostly referring to the main cast, as well as any the most major side or recurring characters. Essentially, characters who occur in more than one episode, make some contribution to the over arching plot, and whose names I can remember without having to look them up.