Ghostzilla is a Web browser like Firefox, but it shows up and disappears instantly, discreetly, blended with your application -- any application -- so the Web pages look like part of it and not like the Web at all. So what's it for then? Entertainment, Ghostzilla is a form of computer art.

What would you use it for?
Hide from your boss and coworkers. Not a good idea; you can get fired (the network administrator sees everything you do) or end up wasting lots of time.
Survive endless meetings (if you have a laptop; kind of like (1) but a little better).
Have a browser instantly available and dismissible within your work application, washed out from ads and unnecessary pictures. This sounds useful -- except it will help you develop that attention deficit disorder. Seriously.