In the first installation of this series I told you, that I think that the command line is the second important tool, to get you faster with your Ubuntu usage. Actually, the command line is the most powerful toy you can use in the Linux world. Today I want to show a terminal emulator that has its root in the ego-shooter Doom. Most Ubuntu-Rockstars have always a terminal window opened, that enables them to punch in some useful and time-saving commands. The drawback of this method is that the terminal is just another application on the desktop and could be hidden behind some different app or could be minimized, that you have to activate it via the window list. An nice alternative is Guake.
Install It
To install Guake you have to download this package from their website and then install it via the Gedebi installer. As with Gnome-Do you should add Guake to your autostart list. After you installed Guake you should hit the systray icon with your right mouse button and choose preference. In the preferences dialog you should set the hotkey for the roll down. I use the Menu-key because I have no further use for it.
Use It
You can imagine Guake like a roller shutter that covers the other windows as you hit the hotkey. 
Now you are free to type in some commands. As soon as you hit the hotkey again Guake rolls up. In contrast to Gnome-Do Guake is not of much use unless you are familiar with the command line. If you are not using the command line already, you should change that as soon as possible. You can find a short introduction here and a useful sheat-cheat here. Discover the opportunities and rock Ubuntu today.