Ha! Those rotary switches are versatile. I have *thought* of a bunch of uses...but so far I have only put one in a guitar. It's in a two HB strat body and I use it to switch between SC and HB settings. So the guitar looks like it has normal Strat controls, but instead of VTT it's V-(4 way rotary)-T.
I like the idea of using a rotary-in-a-box to test ideas before putting them in the actual circuit. I would be useful on pretty much any build.