Well, here is something....
Not sure how one would exploit, but:
Control-Eject: Display Shutdown/Restart/Sleep Dialog
Control-Command_Eject: Restart Immedately (reset)
Control-Command-Option-Eject: Shut Down Immediately
Seems to work on my eMac Ghz G4, even though note is for PM G5.
Also looks like Command-Option-Eject will sleep and wake.