Boss GA-FC Foot Controller
Using the expression pedal sockets on it which take either simple foot switches or expression pedals, I have one simple foot switch dedicated to the solo boost function, and another to turn on the foot controller effect the current patch has. I have a cheap expression pedal plugged into the extra expression pedal socket on the amp, and this gives me wah, pitch blend or whatever I have programmed in.
This GA-FC is the heart of controlling my Katana.