Power Developer Tools

Windows Phone Power Tools (wptools.codeplex.com)

Multilingual App Toolkit (msdn.microsoft.com)

WP8 Emulator Skin Switcher (wp8emulatorskins.codeplex.com)

Isolated Storage Explorer (visualstudiogallery.msdn.microsoft.com)

IsoStoreSpy for Windows Phone (isostorespy.codeplex.com)

XAML Spy (xamlspy.com)

Telerik .NET JustDecompile Decompiler (www.telerik.com)

Audacity: Free sound editor (audacity.sourceforge.net)

Fiddler for web debugging (fiddler2.com)