Drum patterns and colored lights! Use your grid controller with your software synth and keep the LEDs in sync with the GUI. The NeoTrellis MIDI Feedback Controller sends MIDI messages containing note information in order to program a trigger sequencer -- but here's the cool part: when the controller receives MIDI note messages back from the software it interprets them as NeoPixel commands!
Inspired by the excellent, Arduino-based design by PatchworkBoy, this simpler, CircuitPython-based approach will get you started quickly controlling four 16-step drum trigger sequences in a VCV Rack. You can then modify it to fit your needs.