GAC Util location

C:\Program Files\Common Files\Microsoft Shared\Web Server Extensions\14\TEMPLATE\LAYOUTS\Axceler\ControlPoint_Claims
C:\Program Files (x86)\Microsoft SDKs\Windows\v8.0A\bin\NETFX 4.0 Tools
C:\Program Files (x86)\Microsoft SDKs\Windows\v8.0A\bin\NETFX 4.0 Tools\x64
C:\Program Files (x86)\Microsoft SDKs\Windows\v7.0A\Bin


http://ashishkelo.wordpress.com/2012/09/14/gacutil-tips-and-tricks/
http://msdn.microsoft.com/en-us/library/ex0ss12c%28v=vs.80%29.aspx