Ring modulator pedals are a go-to choice for players looking to endow their guitar tone with a robotic, metallic and generally out there effect. By pairing the guitars input with a carrier signal through four diodes, ring mods add a guttural mechanic modulation to your sound unlike anything offered by your everyday delay and tremolo pedals. Popular models include the DOD Gonkulator and the Moog Moogerfooger Ring Modulator.