If you are looking for a perfect manga, this is the one you should totally go for. It's not shonen ai nor yaoi, this is not about romance either (or it's not the main topic); it has everything. It's really good. Action, psychological shit, drama, comedy, love, friendship and fantastic characters that grow up as you read. Really, it's brilliant. I watched the anime version (brotherhood) and I can say it's the best I've seen so far. x
Fullmetal Alchemist