Sam Vimes.
He arrested a dragon. He arrested two armies for "behavior likely to cause a breach in the peace." He's killed werewolves with his bare hands, carries the law with him like a lamp, threw a demonic entity of pure vengeance out of his own soul by raw force of Lawful Good, and is home every night at 6:00 to read to his infant son.
Second place goes to the Doctor, for saving the universe, and Spider Jerusalem, for shooting the President of the United States with bowel disruptor.