Wah tops the list. It’s hard to think of something as “mastered”, because it makes me think there’s nothing else I can get from it. All my pedals are super-simple versions of the type, except maybe the Wampler Ego, and even that one isn’t rocket science; I just don’t deal in subtleties. Weirdly, I feel like I could add my looper pedal to the list, though. It’s pretty simple (Ditto), but I end up mudding up a bunch of layers, poorly-timed, weird volume levels, etc..... It’s just a practice pedal, nothing I use live in any meaningful way, but I think I might need a click for laying down the first layer. Constant reminder of how bad I am at rhythm guitar.