Windows Server 8 (or Windows Server 2012 which is another possible name at release) allows you to remove the server graphical component (or to add it to a server that has had that component removed). At BUILD it was announced that it is possible to convert between the Server Core version of Windows Server 8 and the typical version. This is very different from Windows Server 2008 / 2008 R2 where switching between server core and traditional involves a complete reinstall.
Below is a screencast I created showing the removal and addition of the server GUI component on Windows Server 8.
Follow me on twitter: @orinthomas