Off topic, but it'd be sweet if the movie was called oak-back on account of the lead character's back being as hard as oak. If he had no special skills besides that, he'd have to attack using his back by flinging himslef backwards into enemies, and he'd have to absorb their blows completely with his back. The climax of the movie would be reached when his love interest is tied to the train tracks, forcing him to lie several kilomoters ahead, waiting for the train to hit his oak back and fly off the tracks. This movie just writes itself.