A GuidGen tool similar to the one that ships with VS, but less than a decade old.
GuidGen 2.0 is a new face to creating GUIDs. And includes C#/VB code snippets!
It's also open source!
But a separate app to copy GUIDs from into the editor is still old school. Why not have inline editor completions for GUIDs? Just type "guid" in your C# or VB code files, then click on "Guids" or press Alt+. to select the Guids tab with the keyboard.
Note: The in-editor code completion feature has been temporarily disabled because it has some negative interactions with the language service that I haven't sorted out yet.
Let me know your feedback! Should we get this into a future version of VS?
Download the Visual Studio extension from the Visual Studio Gallery.