ZVex Super Hard On

This is the newer version of the Super Hard on with a zener diode, and is based on Zach's published schematic.

REDDIT UPDATE: Nothing fishy about it, it was the schematic Zach published for the Inventobox and can be seen here: http://www.zvex.com/module_instructions.pdf

Lovepedal COT50

Mosrite Fuzzrite

There's a few versions of this on here now, so just choose the one that best suits the components you're using.

Harmonic Percolator

Mosrite Ge Fuzzrite