Comodo Dragon Internet Browser.

The new version of Comodo Dragon, a Chromium-based browser much like Google Chrome, but with better/more security and privacy options, has an interesting UI. It reminds me a bit of the default Ubuntu Linux look, in that no matter what theme you are using in Windows 7, the title bar is not transparent, and is actually quite dark. The non-focused tabs are nearly unreadable they are so dark!