A driven member of a metal peening machine is disclosed. The metal peening machine is configured to drive the driven member into contact with a work surface of a metal workpiece to deform the metal workpiece. The driven member includes a shaft with an impact end. At least one of a plurality of impact features, an impact feature with a non-flat impact surface, a non-round impact feature, and an asymmetrical impact feature is coupled to and protrudes from the impact end of the shaft. The at least one of the plurality of impact features, the impact feature with a non-flat impact surface, the non-round impact feature, and the asymmetrical impact feature defining at least one impact surface to be driven into contact with the work surface of the metal workpiece.