Here's one that's near & dear to me...Your opinions of the best use of wah-wah in Rock/Prog/Fusion (with examples if you like). Here are some of mine:
Roine Stolt: Every time he uses it, just seems like a natural extension of his playing rather than an "effect". Very expressive & soulful, like it's talking to you...
Jimi Hendrix: Electric Ladyland wouldn't be the same record w/o Jimi's wah work...It's "Still Raining..."
Chet Atkins: Reportedly the first (recorded) user in 1961 (never heard it, but if he used it I'm sure it sounded great...)
Clapton (w/Cream): Disraeli Gears
Zappa: Especially on Roxy & Elsewhere...
Miles Davis: Yup, he used to play his trumpet through one...
Stevie Ray Vaughan: Say What, Voodoo Chile, Come On (Part 3), etc...
Jeff Healey: I remember hearing some really nice textures on See The Light...
Robin Trower: One of my favorite-sounding guitarists...When he combines the Univibe with wah it's awesome...Check out Caledonia, A Tale Untold, Day Of The Eagle, etc...