X-Ray Goggles by Mozilla

Remix and Share Web Pages Instantly.

Allows anyone to “remix” their favorite sites and webpages – changing text, images and other clearly defined elements. Also checkout http://shrturl.co/
Mozilla is taking the Dev Tools interface and making it into a remixing platform. Personally, I might even use this in place of dev tools for pages that I want some extra tooling around my test changes. They are also either brilliant or insane for showing Chrome in their screenshots.