John Heffron's History Rewrite! (New version coming soon with user-chosen websites)
It closes your tabs. It cleans your history. It may even save your butt.
With one quick key command this plugin will close all your open tabs, delete & rewrite your history and even open some new tabs with cool sites. If someone walks in the room you no longer have to fumble for your mouse to click that little "x" to close the browser - BOOM! your history is... history.
How to use: After you've installed, restart your browser and click "Alt+Y" (or "Option+Y" on a Mac) and let History Rewrite do it's thing. One second later it looks like you were browsing some normal sites.
Works with Private Browsing too!