Media Cleaner Pro is a tool that detect unused and useless files from your WordPress. It cleans clean your Media Library and your uploads directory.
It will check if:
You can choose to check your Media Library, your uploads directory, or both. For both of them the plugin will check if the file is in use somewhere in your WordPress. If a file is not in use anywhere (from the uploads directory) but is present in the Media Library, then it will not be marked for deletion. The files detected as unused are added to a specific dashboard where you can choose to trash them. This trash is internal to the plugin and files can be retrieved from it, still through the dashboard. After more testing, you can trash them definitively. Again, this plugin deletes files so be careful. Backup is important!