WP Reset lets you restore everything to default values without reinstalling WordPress or doing it all manually. You can even reset or delete select portions of your site to debug or streamline in record time, including removing all those unused widgets that are slowing you down.
WP Reset comes from the folks at WebFactory Ltd, which is founded by Gordan Orlic. The company has several WordPress products including 301 Redirects Plugin, UnderConstructionPage Plugin, and Google Maps Widget Plugin along with a few others.