I voted for Mustang! FMA will always have a special place in my heart. I also like how Arakawa balanced Mustang’s ambition with humorous moments. His flame alchemy was awesome!
You should read Daemons of the Shadow Realm (Yomi no Tsugai), from the same author, of course, in case you haven't yet.
In a remote mountain village under the watchful eyes of two stone guardians, the young Yuru contentedly lives off the land while staying close to the only family he has left - Asa, his precious twin sister. Asa, meanwhile, carries out a mysterious “duty” on behalf of the village while locked in a cage. Why is Asa a prisoner? And what other secrets does Yuru’s otherwise idyllic home hide?