Holy cow, I wrote a book!
I was able to scream (not whistle: scream)
a 300 baud carrier tone.
This skill proved useful when I was in college and the mainframe
system was down.
Instead of sitting around waiting for the system to come back,
I just went about my regular business around campus.
Every so often, I would go to a nearby
campus phone (like a free public phone but it can only make calls to
other locations on campus), dial the 300 baud dial-up number,
and scream the carrier tone.
If I got a response, that meant that the mainframe was
back online and I should wrap up what I was doing and head back to the lab.
Mind you, this skill isn't very useful nowadays.
What stupid computer talent do you have?