I don't think my 'OC' Homunculus would count. He is not in any story, but he is Lin/Greed. Just in the 2003 Anime.
He makes himself a Homunculus by killing himself (for immortality) and he has an Alchemist human transmute him. He becomes Greed, just the Origanil Greed's memories intact, (His gate opening allows Ed and Al's Return) He works for *Spoiler for After Shamballa Part 3* Dante (who did not die) but he turns on her, and eventually kills her, and possibly himself in the proses.
As I said, not really and Original Character, but he is also not a 'Real' Character.