Re: If you could only have one pedal
Other than a tuner...
Well, I have the overdrive sounds covered with the Mesa amps so, I would probably choose a Crybaby Classic (or a Dunlop Signature Wah, if I found one I liked better) for rock gigs; and then a DOD Hardwire Chorus for jazz and soft rock gigs. I think there are some pedals that do chorus + delay--I'd have to check that out. I use all my pedals about equally...each effect only gets used on about 4-6 songs a night. I like effects; the trick is not to over-use them.
But Stills, Kath, Clapton, Santana, Hendrix...these guys were all terrific Wah users. Nothing in Rock is as FEROCIOUS as a screaming Wah solo.
Bill