My new locale is reasonably flat so I dropped all gears and shifting equipment. I went from a 27-speed MTB in a very hilly area to a single-speed faux pista.

I must say that I like it as there's almost no sound while riding. It's also been great training about learning to learn to spin over a much wider range of cadences.

In CPH, I run a tired 3-speed that's 20+ years old and half rusted away. It's stuck in the largest gear, so I guess that's single-speed as well. But it's much more noisy.