a foot pedal you plug in between the guitar and the amp, as you move your foot it wavers from bass to treble smothly your guitar cry like a baby, with a bit of overdrive these things sound awesome, the dunlop cry baby was played by hendrix, the same as the one in the pic there. the holy grail of wah wah has always been the dunlop crybaby the same as in the picture up there. have a listen to jimmy hendrix voodoo chile. the wah wah is just one of many difrent kinds of effects.
wah wah wah, standin next to a mountain, shot her down with the palm of my hand, wah wah