Sometimes the last thing you, or a user, will want to do is to touch their mouse, trackpad, etc.
As a person who loves using key commands to perform complex actions in a much quicker manner I absolutely love discovering things I don't know.
First off, I've moved on to an awesome new job, and I am now supporting software engineers, server ops folks, and tier 1-3 tech support folks. For the first time I can recall my users are very interested in learning about the underbelly of the Mac OS X GUI and command line. Long story short, this brings me great joy and I'm trying to disseminate my neat hacks to them, starting with running Software Update in the command line (man(8) page here).
Today one of my users was having issues where software was grinding a beefy retina MacBook Pro to a halt. For the longest time I've known about the keystroke for triggering a "halt"/"shutdown -h now" event on older, optical drive equiped Macs (Command Control Option Eject) so I set out to determine the equivalent keystroke for computers lacking an eject key. Pro Tip: sub Power for Eject.
During my research I found this kbase article from Apple, and learned something new. When you hit the Power button on its own you can type R for Restart, S for Sleep, or Return for Shutdown.
For the vast majority of Mac users this will never come in handy. For users adapted to command line environments, who really don't like reaching for their mouse/trackpad, or whose mouse/trackpad is malfunctioning/dead this tiny bit of information is incredibly handy.