Awesome

Unity Sprites And Bones

This is an addon for Unity 3D to create 2D skeletal sprite animations. With the addon its possible to add bone hierarchies directly in the Unity Editor. Sprites can the parented to the bones. The bones can be animated like any other GameObject in the animator window. Inverse Kinematics is also available and animatable. The bones can also be used to animate any GameObject other than sprites like meshes or particle systems.

Features

Skeletons and Bones.
Mesh deformation
Inverse Kinematics with targets.
IK Helper objects.
IK Angle Constraints.
Bones and IK are fully animatable.
Bones can be added by holding Ctrl and left clicking.
Bone splitting (Subdivision).
Flip Skeletons and Bones on X or Y Axis at the push of a button.
Mesh creation for Skinnable Meshes using custom mesh creation tools. Meshes are saved as assets.
Free Form Deformation using control points.
Shaders that support shadows and z-zorting (can be customized per Skeleton).
Scaling of root object of Skeleton.
Saving and loading of poses. Poses are saved as assets.
Helper tools to sort render layers, copy positions and rotations between objects, and create materials for renderers.
2D Ragdoll creation.
Fully integrated in the Unity Editor.
Undo-Support
Lots of gizmos!
Did I mention Inverse Kinematics?
Free and Opensource

Screenshots:

Forum thread:

http://forum.unity3d.com/threads/219915-Release-Free-Unity-Sprites-And-Bones-2D-skeleton-animation

Tutorial read the 2DSkeletalAnimation.pdf for an explanation of how to set up and use this tool.

Demo of how to use sprites and bones with this fork:

Installation

After importing into a new project, the Gizmo folder has to be moved to the Asset folder. Otherwise some icons won't show up in the editor and the hierarchy.