Recently I wanted to test the a keyboard shortcut, which is supposed to kill X server (hence very useful when you have a crash). That shortcut is not dependent on any particular window manager (like lxde, unity, kwin etc). So, it must work, even when you have unresponsive window manager (as opposed to Alt+Ctrl+Backspace which kills the session, and bring you a login screen).

That's why I interested to make my WM (unity) unresponsive. Is past, it was very easy. Opening a terminal, typing unity --replace and then force close the terminal, was the simplest procedure. But unfortunately, This is not true in Ubuntu 12.04, (they make it very robust) Because whenever I kill the terminal, Unity automagically restart itself. I also tried compiz --replace but wasn't successful.

My question is: How can I make Unity unresponsive while I am in Unity session, so that window manager does not recognize any keyboard shortcut.