Just for fun: what are some UI that have surprised/impressed you?

A recent post titled "What makes you choose Mac?" inspired me to think of all the little Apple touches that I've come to enjoy and expect over the years. There are many "big" reasons why I like Apple devices, but these little touches add up and they are undeniably a part of why I like Apple products. They can just be details, or clever UI. There are many more than I've listed here, just that I can't really think of all of them right now.

On iOS:

1. The normal lockscreen has the fade-in effect. When music playback controls are displayed, the screen turns on instantly.

2. When setting a lock-screen wallpaper, the area where the time is displayed is darkened/shadowed to improve the legibility of the text.

On OS X:

1. Search in the Settings app is pure genius. When I type something, the relevant sections are spotlighted. Wow. Aesthetically pleasing, instantly understandable, and powerful.

2. Download stacks. It makes so much sense to put this as a default stack in the dock. When I download something, the file flies over to the stack. Again, it's so intuitive and useful.

3. Dock icons bounce for attention. Clever and fun!

Please share yours!