Seymour Duncan Tweak Fuzz
 

Just picked one of these up used cause the price was right. It's made for guitar. Basically a fuzz face with a 6 way switch that rolls off lows. I removed the output cap (C2 on the schematic) and put in a 0.22uF cap. I suspect 0.47 would be even better. Pretty usable bass fuzz now. I'm going to do the volume mod next.