MXR M103 Blue Box Octave Fuzz Pedal
The Blue Box from MXR fuzzes out your tone and then drops it two octaves. The Blend knob lets you mix between dry and effected signals. Turning it all the way up (100% effect) gives you a lively and chaotic lo-fi fuzz sound. Rolling towards the dry signal gives you a little more control, and gives more recognizable tones.