Electro Harmonix 8-Step Program

I use it to control the delay time of an analog delay pedal (Supro).

My delay pedal sounds really different with different modulation settings via this pedal. Even different when the depth and rate are the same but the sliders forming a different shape. The differences can be subtle: triangle vs sine wave. Or more different by using sawtooth shape.
Or think about 7 sliders on one position and 1 at a very different one. Then when the sequence hits that 1, then the sound of the delay suddenly detunes the guitar sound, fun!

But, you must love turning knobs (slide sliders) and thinking about this kind of things. If you love pedals with 1 knob, don't go this route.