The first thing I usually do after booting my Linux machine is to fire up terminal and keep it there. Every now and then I might be looking for something, do a quick tweak or even write into a text file, it's handy with the terminal.
One of my favorite terminal emulator is Terminator. It's a nice piece of art that enables you to split your window.
However, recently I stumbled upon drop-down terminals & I installed Guake. I instantly fell in love with it (^^,) ...
Guake runs in the background and can be invoked using keyboard shortcuts. By default, F12 to toggle visibility and F11 for full-screen.
Transparency, keyboard shortcuts etc can be adjusted using the Guake Preferences tool.