Is there a way to force Mac OS X to close all the applications when restarting?
All you need is to open Terminal.app and type:

sudo shutdown now


That way the system will be forced to terminate all open programs, ignoring any unsaved file changes.

So, in order to be able to launch it via the desktop, you need to open Applescript editor, and type:

do shell script "shutdown now" with administrator privileges


Save the script as an Application, and drag it in your Dock, or somewhere where you'll find it instantly.