The totally unnecessary but really cool things that Android can do!

I was on Android Police and I came across this app/live wallpaper:

It takes the music playing in the background (and even system sounds) and visualizes the music as a live wallpaper. Is it indispensable? Is it the best thing ever? Does it add any utility other than some flashy graphics? No! But it is so pretty and mesmerising and something only Android can do among the dominant mobile OSes right now - it made me happy to be using the GS2. It made me smile.

Do you have any totally unexpected moments of delight that you suddenly came across while using your Android device?