Asset|Preview is an essential tool for any level designer with a lot of assets in their project!
The tool is made for quickly and painlessly previewing and instantiating meshes, prefabs, textures, materials and audio into your scenes.
Instead of going through the project view where you have to remember what the particular asset you want is named, you just quickly and visually find it in Asset|Preview, click it, and it's instantly placed into your scene!
(Actual assets seen in the screenshots not included)