Howie's Metal Simplex
I found the schematic for this at DIYstompboxes and thought I'd give it a go. I think "Metal" is a bit of an exaggeration, but it sounds pretty good considering the low parts count.
The circuit appears to be a simple common emitter boost pushing a bazz fuss. The tone control is a simple high-cut filter, but it does the job.
Feel free to experiment with the diode type. The original specifies LED.
Also, using a higher value gain pot gives more gain in the first stage, which means more dirt. A 500K pot provides a decent boost in overall clipping, and allows for easy pinch harmonics. I have not tried 1M yet, but I suspect it would only give a tiny bit more grunt that the 500K.