Requires Unity 5, any license. Works on both the Mac and Windows versions of the editor. Comes with full access to the source code.
Tired of manually applying the same import settings to your audio clips, textures, and models again and again?
Default Import Settings uses an asset you specify as a template, and then automatically applies the import settings of that asset onto new assets dragged into the project.
Just go to Assets -> Default Import Settings, drag your template assets in, select which properties you want to include in your defaults, and you're good to go.
If you want to apply the defaults to already imported assets, you can do that as well by selecting the assets you want modified in your Project view and then pressing one of the Apply Defaults buttons (all three types of assets, or audio/models/textures only).
Default Import Settings exposes the writable variables in the AudioImporter, ModelImporter, and TextureImporter classes. As long as you only need a single template for each asset type, you'll never need to write your own asset preprocessor again.
The defaultSampleSettings variable in AudioImporter is not included in the dropdown list of properties because it causes buggy behaviour in the editor when set.