All your friends use Skype, but you've found an application much better than Skype. You ask you coworkers why they still use Windows Explorer to go to a specific folder. Nobody wants to listen when you say that the Start Menu is useless or that you spend most of your time using the command-line.
If you use a software with little or no awareness and you're proud of that, tell the world about it. Don't forget to mention why you think it's special. It doesn't have to be a Windows software, but it would be nice if it were free.
Some of my underground software:
FreeRAM XP Pro - optimize your RAM
Super - convert multimedia files
Total Commander - Windows Explorer is nothing