I just made a fresh upgrade to Mountain Lion on my Macbook Air and the first thing that I noticed was the Macintosh HD drive appearing on my desktop.

Although I admit that when it comes to usability, shortcuts are useful. But for some reason I believe the Macintosh HD icon appearing on the desktop just interferes with the clean design and decided to get rid of it, here are the steps.
- Click on Finder and open Finder's preferences pane.
- There in General tab, uncheck "Hard disks" under "Show these items on the desktop" to clear away the icon.
That's it. The same can be done to remove icons of external disks, connected servers or any CDs, DVDs and iPods connected to your Mac.