I have two favorites. One is definitely the ZVex Wah Probe. It is also my favorite of the Probe series. It's neat, because you can tweak it more than most basic wahs.I've had a Zvex Wah Probe for about 18 years. Its not a traditional wah but its cool as heck. I can get fairly traditional sounds out of and of course fairly unique depending on if you use your foot or your hand. It uses an RF frequency to sense the water in your blood.
My other favorite is the Maestro Boomerang Wah. It is great for getting scratchy filtered 70s Krautrock sounds. If you want the sound of Neu, this is it! The only problems: It is highly susceptible to RF interference. All you will hear is local radio. It is likely nowhere near true bypass or noiseless, but, who cares. It's awesome.