The family of distortion devices is very large, but the hardest nut to crack is to find a good fuzz. Of course there are gazillions of fuzzes out there, but only a bunch of them sound really good. Often they are too shrill sounding with not enough bass and mids plus they compress the sound very much. The solution is simple: one needs a good design and to learn to not to turn the gain all the way up. For bass guitars the situation is even worse, with most fuzzes the body of the bass sound is gone. Of course there are some good designs too, one of them is the Zvex Wooly Mammoth. It can be used with guitars too, but it really starts to shine with bass guitars. It is a Fuzz Face relative with some added extras.
The “Fuzz Faciness” can be seen on the schematic too. The additional two pots make the effect more versatile. Many transistor types can be used, for me the 2N3904s sounded best.