Google+ - When searching, the page indicator arrow slides from the left side to the top.
/via Vedran Židanik
Square card case iPhone app - Credit card form that shows card type and flips around when you get to the security code on the back.
via Matt Bilson
AirDrop - The icon changes from a package with a parachute to a radar when selected.
Twitter for iPad - Swiping your timeline to the right, removes the content layer. It’s visualized by a little animation behind the timeline.