Boss Key permits you to hide immediatlly active program window using a hot key! Everybody should have such program for personal security.
Imagine, you work with confidential information - maybe, just writing email to your girlfriend, or entering your credit card information, or typing password to login somewhere, or,maybe, working with CIA files<g>. WARNING! Someone comes to you. What will you do?

Close program? - are you sure you can do it really fast? And don't forget about 'Do you want to save' dialogs!

Switch off your monitor? - yeah, it's very ... very fast! And certainly your visitor will like that you trust him so much! <g>

Reboot your PC? - great decision! Excepting that all your work will be LOST!
Or just do nothing? - congratulations! Now you are absolutely free man - you have no secrets!

Press F10 (or any other key you assigned) and it will be IMMEDIATELY hidden. After your visitor went out press it again and continue working