A Fly!

Trick people into believing that there is a real fly on your computer screen.
When you open this widget, right click on the fly and select "always on top".

This will hide the fly button on your taskbar. It will also prevent your fly from being cover up when you are using a window.

To be really convincing that this is a fly, scroll up and down on a webpage (the fly will remain where it is). If you think the fly is too big just click on the fly and zoom out (numpad minus) to make it smaller (Thanks tinhoy for this hint).