Recently I bought a cool fan, the Revoltec LightWriter. I have a server machine and the frontside of case is open, directly behind that space you can see all the harddrives. To keep the harddrives cool I first had a high end Papst fan running. At one of the local computershops, iComputers, I saw this really great Revoltec LightWriter.
It has LEDs on the blades of the fan and by spinning them around quickly it writes texts in the air, like “Reboot Your Mind”. The nicest thing is that it also writes the incoming air temperature.