More low end than your neighbor's lowrider, the MXR M-103 Blue Box Fuzz Octave pedal will scream its way into your heart. Fuzz and two octave down duplication makes the wet signal from the MXR M-103 Blue Box Fuzz pedal chaotic yet friendly.
The MXR M182 El Grande is a lovely little bass fuzz pedal based on classic 70's style fuzz pedals. The El Grande was then tuned to lower frequencies and given a Deep switch for even more bass. Check out the MXR M182 El Grande Bass Fuzz Pedal.