Recently working a lot with JSON data. Needed a debugger visualizer for JSON. Found one at: http://jsonviewer.codeplex.com/
Copy contents of the visualizer folder in the zip package to VisualStudioInstallPath\Common7\Packages\Debugger\Visualizers (on my machine this is C:\Program Files (x86)\Microsoft Visual Studio 11.0\Common7\Packages\Debugger\Visualizers) and working! See http://msdn.microsoft.com/en-us/library/sb2yca43(v=vs.110).aspx for other instalation options.