The Show Desktop Button
Back in the late 90's, Microsoft rolled out a feature as a part of Windows 98 that I have come to love far and away above all others. It was a simple feature that 85% or more of folks don't even know exists. If they have seen it, chances are they've never used it and don't know what it does.
I am speaking of the "Show Desktop" button.
What does this button look like?
Below are the icons for the Show Desktop button for Windows XP and Windows Vista, respectively.