DigiTech Drop Polyphonic Drop Tune Pitch-Shifter

They say:

The DigiTech® Drop is a dedicated polyphonic drop tune pedal that allows you to drop your tuning from one semitone all the way down to a full octave. Get down-tuned chunk without having to change guitars! The Drop also features a momentary/latching switch. With the switch set to momentary, you can turn the Drop into a true performance pedal. Fast trills and roller-coaster pitch dips are at the tip of your toes.

9 DROP SETTINGS

Allows you to drop your tuning from one semitone all the way down to a full octave. Drop range: 1-7 Semi-tones down, Octave down, Octave down + dry.

TRUE BYPASS CIRCUITRY

Preserves your tone when the pedal is not in use.