I really like the Ibanez WH-10 version 2. John Frusciante has long used the original version and I switched from the standard Cry baby to it and I'll never go back. Man the WH-10 has a bass and guitar mode that places the wah in different frequencies. It also has an adjustable decibel boost that you can use to drive the signal when you switch the wah on, which I really like. This wah also has more range/sweep to me, and is more snarly to me.

to hear the "snarl" Im talking about, listen to the first bit of this: