The Marshall Jackhammer JH-1 is a discontinued guitar effect pedal that provides overdrive and distortion tones, designed to emulate the sound of a high-gain Marshall amp. It is known for its versatility with a mode switch for overdrive or distortion and a "Contour" control for shaping the midrange. While the distortion mode can get very heavy, some users find it can be muddy and bass-heavy, while the overdrive mode is praised for being dynamic and versatile.