What is a wah-wah?
Wah-wah is an effect that alters the tone of the guitar, kind of mimicking a human voice, just like trombone or trumpet players does with the aid of moving a mute into their instrument´s bell. The guitar pedal is created with a rocking switch that is connected to a potentiometer which decides which way the tone should go. The creation of the wah-wah is a good old accident at the Thomas Organ Company back in 1966. They were re-designing a Vox amp from a tube amp to a cheaper solid state amp, and therefore replaced the expensive Jennings 3-position MRB circuit switch with a cheaper transistorized solid state MRB circuit. This caused an altered tone to the speaker, so when the folks at the company connected a volume pedal to the circuit the wah-wah pedal was born. First the company thought of the effect to be used by wind instruments, like the saxophone, before guitarist Del Casher suggested that it shoud be used on the electric guitar. Good call, Del Casher!
Any good examples?
Two guitarist's who where among the first to use the wah-wah pedal was Eric Clapton and Jimi Hendrix (turned on to it by another wah-lover, Frank Zappa). Listen to songs like "White Room" (Cream), "Voodoo Child (Slight Return" (Hendrix) or "Peaches En Regalia" (Zappa) for good examples. Also the funk guitar depends a lot on the wacka-wacka sound of the wah-wah, Isaac Hayes song "Shaft" is a great example. Chicago guitarist Terry Kath was another proud user of the wah-wah which can be heard in songs like "25 or 6 to 4" and "Skin Tight". There´s plenty of hard rock and metal guitarists that uses the wah-wah as well, like Tony Iommi of Black Sabbath ("Turn Up The Night"), Kirk Hammett of Metallica ("Enter Sandman") Slash of Guns N' Roses ("Sweet Child O' Mine") and Zakk Wylde ("Gets Me Through" by Ozzy Osbourne). Names in alternative rock and pop includes Mike McCready of Pearl Jam ("Even Flow"), Kim Thayil of Soundgarden ("Black Hole Sun"), Gaz Coombes of Supergrass ("Hollow Little Reign") and Crispian Mills of Kula Shaker ("Grateful When You're Dead"). And of course blues player's also likes the wah-wah, listen for example to Joe Bonamassa ("Pain And Sorrow") or Kenny Wayne Shepherd ("Blue On Black"). The wah-wah can be heard almost everywhere in music, at least where there´s a guitarist involved.
Which pedal should I get?
There´s some obvious, classic choices as well as some more modern takes on the wah-wah pedal that could be interesting. The Dunlop Crybaby is a classic with many options - the standard GCB95, all the signature models (Zakk Wylde, Dimebag, Jerry Cantrell,Bonamassa, Slash...) which often comes with a knob to set the sweeping level, and the 95Q which has the great feature that turns on the effect when you put your foot on the pedal and turns it off when your foot is no longer resting on the pedal. Vox also makes some classic wah-wah pedals (it would be strange if they didn't when it was their accident that created the sound). For an example their V846 is a great handwired pedal, for another check out the Joe Satriani model Big Bad Wah. Steve Vai also has his own line, produced by Morley, called Bad Horsie (yes, after the Vai song whch involves plenty of wah-wah). The Bad Horsie has the same "touch" feature as the Dunlop Crybaby 95Q, something the people at Morley calls switchless design, which I think is a great advantage. For some more expensive and more exclusive pedals, check out the Jam Wahco Plus or the Roger Mayer Vision Wah. The latter was created by Mayer, pedal maker for Jimi Hendrix, and according to him this pedal does not only sound great, its design also gives the user a more ergonomic feeling. But before you spend all your money on a really expensive unit, check out the classics - they're usually classics because they're really good.