Michael Fassbender, the man people are currently touting as the greatest actor of this generation. He already did great when he starred in X-Men: First Class, and will be flexing his assassin skills in the Assassin’s Creed film too.
He has a particular screen presence that is very commanding. He made an excellent adversary as Magneto and those qualities would carry over well to the Bat. His natural good looks and undeniable confidence should help on the Bruce Wayne side of things and at 6 feet, he definitely looks imposing.