A very nice idea from my friend Laurent:
Using the predefined buttons styles for the ApplicationBar in Windows 8 When you create a new Windows 8 application, the Common folder contains a file named StandardStyles.xaml. Amongst other styling resources, this file contains a trove of application bar buttons styles, including Microsoft Design-like icons. In order to use these styles, however, you need to uncomment the corresponding one. Microsoft commented these styles out, because otherwise they would be instantiated by the XAML parser when the app starts, which would cause some delays and use unnecessary memory. That makes it a bit tricky to find the right button style you want to use for your app bar. To make things a little easier, I made an app that you can download and run.