Here's the sourcecode for all builtin Unity shaders (always at latest version): http://unity3d.com/download_unity/builtin_shaders.zip
Unity 1.6.2 shaders, if you still need them, are here: http://unity3d.com/download_unity/bu...ders-1.6.2.zip
The sourcecode is provided as a reference and for learning purposes. You don't need to put the shaders into your project; they're all builtin. If you do, be sure to modify shader name at start of the file, otherwise names will collide with the builtins.
Also checkout UnityCG.cginc and AutoLight.cginc in Unity.app/Contents/CGIncludes - the builtin shaders use some helper functions/macros/variables from there.