Here's a cool auto wah from Robert Penfold that can sound really funky and bubbly.
In the soundclip the resonance and depth are maxed.
I have adapted it for true bypass and added a volume pot since the output was alittle bit above unity. The controls are a bit finicky, especially the frequency controls that goes from low (so low that it kills the signal) to above the hearing range. I think a log pot work better here. I used a 2M resistor insted of the 1.8M and a BC108B transistor with good results. The 10K trimpot sets the input for the envelope follower. Adjust it until it sounds good and you get a "natural" sounding release.
All the layouts are Verified unless noted.