Windows 8 App Bar Icons (from Segoe UI)
UPDATE: since writing this I've found this MSDN article that I think has more information than my post. Hope that's helpful.
This is a reference post. Come back when you, like me, forget which icons are available to use on your application bar in your Windows 8 app.
If you define your app bar imperatively (in JavaScript), then you would simply pass the name of the icon from this graphic in as the icon option like so…
new WinJS.UI.AppBarCommand({..., icon:'bookmarks', ...})
Here’s the chart for those with young eyes :)