Besides the 2D sprite system, Unity has created and updated their animation to handle 2D. With a greatly enhanced dope sheet animation/clip controller and full integration with the Mecanim state management system, there is a boundless world of choices available that are easy to use once you get to grips with them.
All of the animation in the new 2D system in Unity uses the new Mecanim system (introduced in Version 4) for design and control, which once you get used to is very simple and easy to use.
It is broken up into three main parts: animation controllers, animation clips, and animator components.
Animation controllers are simply state machines that are used to control when an animation should be played and how often, including what conditions control the transition between each state. In the new 2D system, there must be at least one controller per animation for it to play, and controllers can contain many animations as you can see...