Holy cow, I wrote a book!
When you select "Shut Down" from the Start menu,
a dialog appears with three options:
"Stand By", "Turn Off" and "Restart".
To get the secret fourth option "Hibernate" you have
to press the shift key.
Would the Alt key be the more obvious choice for
revealing alternate options?
You might think so, but it so happens that Alt already
In this dialog, the Alt key would be a disaster,
because the underlined letters indicate keyboard
accelerators, which are pressed in conjunction with the Alt
In other words, from the Shut Down dialog,
you can type Alt+S to stand by, Alt+U to turn off,
or Alt+R to restart.
Since the Alt key was already taken,
the Shift key had to be used to reveal the bonus options.
Using the Shift key to reveal bonus options is not uncommon.
You can hold the Shift key while right-clicking on a file
an extended context menu,
and of course there's the Shift+No option in file copy
dialogs to mean "No to all".
In fact, you don't need to press the Alt or Shift keys at all.
Recall that the rules for dialog box navigation permit omitting
the Alt key if the focus control does not accept character
input; since the only things on the Shut Down dialog are
pushbuttons, there is no character input and you can just press
"S", "U" or "R" without the Alt key.
What's more, you don't need to hold the Shift key if you want
to shut down; you can just type "H" and the Hibernate option
will be invoked,
because hotkeys for hidden controls are still active.