Wild, unpredictable fuzz tone you control like a theremin.
The Fuzz Probe from ZVex is like a cross between a theremin and a Fuzz Factory pedal, controlled by tweaking its Stability knob and interacting with the pedal's RF field with your foot. There is a 3-5/8" copper plate mounted on a chunk of 3/8" clear acrylic that passes over the top of the pedal housing, angles down to sharp turn, and goes back to the pedal. Under the whole mess is a 3-5/8" x 7" sheet of aluminum that provides shielding from annoying ground effects and wires under the stage. It also serves to protect the knobs from being knocked off if you drop it on them, and it makes a nice toe chopper if you are barefoot, so here's the legal disclaimer: don't drop the Fuzz Probe on your foot, small children, or animals.
The Fuzz Probe's copper antenna projects a field of RF energy that is affected by your foot, altering the circuit that generates it, and in so doing, increasing the brightness of the LED on the top of the ZVex pedal, also controlling the Stability (Stab) knob on the back. This control lets you select your favorite squealing Fuzz Factory setting and then mess around with the Stab knob with your foot and create little melodies and interference modulations with your guitar.
To get the widest range for the probe control, be sure to leave the Stab knob on 7 o'clock. The Probe adjusts the Stab knob from wherever it is set, upwards toward the most clockwise position as you get closer to the antenna. It you set the fuzz pedal's Stab knob more clockwise, the Probe will let you raise that pitch up to the top as you get closer.
Note: Due to the nature of each hand-painted Fuzz Probe pedal, there may be a slight difference in design from the posted image.