Turn On/Off Windows Server 2012 GUI with PowerShell

Turn GUI Off with PowerShell

Get-WindowsFeature *gui* | Uninstall-WindowsFeature –Restart
Once rebooted, you will only have the command line and no GUI

Turn GUI On with PowerShell

Get-WindowsFeature Server-Gui-Mgmt-Infra, Server-Gui-Shell | Install-WindowsFeature –restart
Once rebooted, you will have the GUI