I’ll add to this list from time to time.

WP Reset

WP Reset By WebFactory Ltd resets the database and deletes posts, pages, comments, and every user except the one logged in. It does not deletes the media files, nor plugins, themes, or uploads.

Plugins Garbage Collector

Plugins Garbage Collector by By Vladimir Garagulya – scans the database and finds orphaned rows that have no corresponding plugin.