Just finished a 3 day or less project, but not a Guitar PCB pedal. I quickly built a Guv ‘nor style pedal with a tone mod of sorts.  I used sockets for a resistor and a potential capacitor, which I can switch out components to quickly mod the treble content of the pedal.

The mod can be seen in the upper right hand portion of the board with an empty socket for a potential 10n capacitor addition and a socketed transistor.