Charlie,
Dave (the founder and genius behind Function FX) is a friend of mine. The Clusterfuzz is a pretty amazing pedal capable of an unbelievable assortment of fuzz tones. It's a bit too 'tweakable' for me, though. He makes a much simpler silicone based fuzz pedal called the End of the World Fuzz exclusively for a shop in the Chicago Suburbs. It is my favorite fuzz of all time. It delivers such a thick, rich and organic tone that stacks up against the best from the 60's and 70's, but can be rolled back for a much more tame overdriven sound. I AB'd it against well over a dozen different fuzz pedals at Chicago Music Exchange and for me nothing even came close. My favorite prior to that was the Frantone Sweet, which they don't make anymore. I'm a guitarist, so clearly our needs are different. I gave one of the End of the World pedals to my son's bass instructor - a semi-professional player who teaches at our School of Rock. After trying a number of different pedals, he found this was far and away the best sounding fuzz for bass that he'd come across. It's also in a tiny enclosure the size of the Xotic EP Boost and SL Drive, so if space on your board is limited, it's perfect. Just my $0.02.