Bob Bradshaw's creation -  a favourite of the shop -=- watch the video and get the reason why this is a must for your pedal board. 

Custom Audio Electronics -  WAH  MC404
The CAE Wah allows you to switch between two distinctly-voiced Fasel® Inductors with a built-in Boost/Line Driver circuit, internal Q and gain controls, and bright status LEDs on each side of the pedal.
The MC404 CAE Wah was developed by Bob Bradshaw of Custom Audio Electronics and the Cry Baby design team with the goal of creating a highly versatile wah-wah of top-grade components. It features dual Fasel inductors with two distinct voices (high-end emphasis or low to mid resonance), and a built-in MXR MC401 Boost/LineDriver adds even more flexibility. Choose between inductors and turn the boost on or off with the side-mounted kickswitches; bright LEDs on each side of the wah indicate operation status. The MC404 boasts true hardwire bypass, a long-life CTS potentiometer, and internal pots for Q and gain adjustments.