1. AssetpathattributeAssetPathAttribute is a Unity attribute used in Unity to allow you to have drag and drop asset references in the inspector but really use string paths for serialization.
2. WeaverWeaver is a code weaving framework built right into Unity Engine. Based heavily off of Fody.
3. IpoolIPool is an open source Unity pooling system. It's designed to be easy to use and full docmented.
4. UnityIOAn easy to use API that allows you to manipulate files inside of Unity without the headache of using AssetDatabase.
5. ScriptForgeA simple tool to generate constants for Unity for your Layers, Tags, Sorting Layers, Animations, Scenes, and Resources.