In Visual Studio 2010, there was a Create GUID entry in the Tools menu. I used it all the time for SharePoint Development.
Has Tools > Create GUID been removed in Visua
No it's there... at least it's available in Visual Studio 2012 Ultimate.
If missing try adding it via Tools -> External Tools and add:
%Installation Path%\Microsoft Visual Studio 11.0\Common7\Tools\guidgen.exe
EDIT: It's probably installed with Visual C++.