Right click on a empty area on desktop, and click on New and Shortcut.
Type this location into the location area, and click on the Next button: shutdown.exe -s -t 00 -f
NOTE: Subsitute 00 in the command above with a number between 0-315360000 for how many seconds you want the time-out period to be before the computer shuts down.
Type Shut Down Computer for the name, and click on the Finish button. NOTE: You can name this anything you like.
Right click on the new Shut Down Computer shortcut on the Desktop and click on Properties.
Click on the Shortcut tab, then click on the Change Icon button.
Click on OK.
Select the icon of your choice and click on OK. Click OK again.
That's it. This will set an instant shutdown.exe shortcut on your desktop.
EDIT TO ADD: I would advise against using this shortcut if you use "single click" in folder options or pinning this to the taskbar, for obvious reasons.
2nd Edit: Ran the shutdown shortcut with UAC cranked all the way up, no prompt.
Edited by Union_Thug, 19 September 2011 - 01:33 PM.