Unity3d-4.x-Sprites-Opaque-Shader
Unity3D doesn't come with a shader for opaque sprites. The Sprites-Default shader always render sprites by calculating transparency, regardless if your sprite is transparent or not. A simple test showed that my opaque sprite shader is 30% faster than the default sprite shader. The test was made with only one sprite. I believe the performance gain is much greater than 30% in cases where you would have several layers of sprites. I'm really not good with shaders so I just modified the Sprites-Default shader. Feel free to contribute if you can optimize this further.