Amp in a box! The JUDGE GD20 in a pedal. Use a 9v source to use as a standard pedal. Use an 18v supply to get a line out to feed a power amp or into the effects return jack of your amp. 
We use JFETS to mimic the gain structure and tone stack of our GD20 amp. 
 
Great clean, overdriven, or somewhere in between.