The Boss OC-3 SUPER Octave borrows sounds from its predecessor the OC-2, but unlike any other octave it is the world's first compact pedal with true polyphonic octave effects. For the coolest octave around try the Boss OC-3 SUPER Octave.
The Boss MO-2 Multi Overtone enhances your guitar's overtones. The MO-2 boosts the natural second and third generation frequencies to create 3 different harmonic profiles, with or without a substantial layer of pitch-shifting modulation.
The Blackout Effectors Crystal Dagger is an effect like you've never heard. Putting together an octave fuzz with a ring-mod/phase circuit produces some interesting results and the Blackout Effectors Crystal Dagger does just that.