Fireman. While I have a deep sense of justice, there is a melding of simplicity of purpose and action in being a fireman. A policeman's work is fraught with complexities, and tough moral pills to swallow.
Random mutation: Would you rather have wings or gills?
Would you rather have super-strength or super-speed?
(On policemen/firemen... I've had firemen tell me that very few people are happy to have the police arrive at their home, but they're almost always glad that the firemen are there, even if they're called for a bad situation.)