I've been using
a .05 capacitor on a 250 linear taper tone pot for years.
It generally makes the overall tone a bit muddy, which I personally like, but I've had complaints from people who've played it.
It allows an "oo-um" sort of wah noise, with a sweet spot notch that kinda makes the guitar sound like it's blowing it's nose... This is with a single humbucker.
Leo's original Esquire switching had a feature similar to this, with one of the positions bypassing the tone pot and going through a 1MFD capacitor to make a bassy sound. Switching back and forth would supposedly create a "wah" effect, I guess.
"If you haven't had an Accidental Dischord recently, then you are due for one. There is no such thing as an unloaded guitar"