Outside of a tuner, next is a ge Treble Booster, most frequently a Keeley Java, though AM Beanos, and a Union Tube and Transistor have been the one at times. It's pretty much an always on pedal in most permutations of my rig for almost 20 yrs.
It extends the usefulness of my neck pickup quite a bit, and is usually cranked with clean to mean controlled via guitar volume. It's also used as a boost into a thick fuzz or distortion for my main high gain tones.