Audiosurf for me. Just listening to my favorite mp3s and not really caring if I set a new world record or not.
In the same vein, doing a job in American Truck Simulator or Euro Truck Simulator 2. Just chilling out, driving across the map to deliver cows or whatever.
Audiosurf 2 exists, but I’ve never tried it. There’s something soothing about the old-school Audiosurf I quite enjoy.