John Mayer uses Vertex Axis wah

The Axis Wah is the finest representation of a vintage Wah Wah pedal. The pedal is designed to produce the most vowel-like and vocal characteristics synonymous with Wah Wah pedals from the 1960′s. The Axis Wah uses a custom, hand-wound Halo inductor, and hand-picked components to give this pedal its distinctive voice.