No 3D preview. You need to export to FBX/OBJ to view models externally. 3. DevX Unity Asset Viewer (Online / Web-Based) Platform: Any browser Cost: Freemium
UABE is more technical than AssetStudio but offers unique capabilities—it can assets, not just view them. unity3d file viewer
Noesis is not a Unity-specific tool, but it supports dozens of game formats, including many Unity container files. It excels at with full texture mapping and animation playback. No 3D preview