Benjamin "Lefty" Ruggiero. He wasn't a Don, hell, he wasnt even a capo, but he honored the law of omerta. That is one of the most important things in being in the Mafia. He did his prison term, didn't rat to anyone to reduce it, and he didn't sell out to the movie producers for Donnie Brasco(Great movie by the way) when they offered him money to appear in ads for the movie. He was, in my opinion, a true mafioso .