Somehow people here are hyped about classic Skeumorphism iOS app design example again, but here is my all-time favorite no one seemingly has mentioned.

There used to be an app called "Steinway Metronome" It is a simple metronome app, but insanely beautiful with a craftmanship. You could even change the wood finish type.

This app literally inspired the teenager me a lot. If you remember about this, we can be a friend.