MINE for Facebook
Unlike Twitter, Facebook has said it has no plans to build a Windows 8 app. The native People and Messaging apps offer some basic Facebook integration, but they're no substitute for a full-blown Facebook app. MINE for Facebook is the best alternative app available at the moment, offering a customizable view of your Facebook feed, notifications, and your friends’ profile pages. You can also update your status, leave comments, share links and pictures, and more.
It doesn’t replace the Facebook website entirely, though—you’ll still have to use the Facebook website to milk cows in FarmVille.