What do you mean by "power-save" mode really? Any of the presented options do not account for suspend or hibernation states. So, no cookie for you, pollster.
Now, if "monitor" or "screen" were inserted somewhere, i would choose something from the below depending on my own state of mind ...
- Moving the mouse around wildly
- Clicking one of the mouse buttons
- Pounding the keyboard
- Pressing the shift key
- Pressing the spacebar
- Pressing another key which I believe will not affect any open programs or windows
- Pressing any key, not caring if it affects any open programs or windows