We are currently testing Windows Server 2012 R2 Server Core, which does not have a GUI, as such. The server just boots into cmd.exe (i.e., NT-DOS) and has a much smaller attack surface (and less patching) because most GUI components are not on the server. However, GUI fundamentals are there. For example, cmd.exe, Task Manager, and Notepad launch in a Window on Server Core.
One thing "missing" in Server Core is Windows Explorer, and our tightly locked down environment sometimes prevents the use of the Admin shares, i.e., C$, D$, etc. from a remote machine. Consequently, there are times when a File Manager of some sort would be useful for managing the file system locally on the Server Core server.
PowerShell has the ability to present GUI applets to the user on Server Core. (Please see http://blogs.technet.com/b/heyscriptingguy/archive/2011/07/24/create-a-simple-graphical-interface-for-a-powershell-script.aspx which contains the code for HELPDESK.PS1, which opens a GUI with a clickable button.)
Also, I copied an old PowerShell script (based on Sapien's PrimalForms Community Edition) that I wrote a few years ago to one of our Server Core boxes. The script opens a GUI window, prompts for a SQL Server database connection string, and displays database session data in a list box. A "Refresh Data" button requeries the database and refreshes the screen. The script seems to work fine on Server Core; so, the basic elements of GUI window painting appear to be present in PowerShell 4, which ships with Windows Server 2012 R2 Server Core.
As I recall, Sapien's PrimalForms Community Edition also touted the ability to display and process mouse clicks with PowerShell. (If I recall correctly, it claimed to have the ability to use PowerShell mouse clicks to expand nodes in a GUI display tree, which would be analogous to double clicking a folder in Windows Explorer to get the folder to expand.) However, it looked complicated, and I never got around to trying it.
So..., has anyone found a Windows Explorer workalike PowerShell script for Server Core?