Productivity on Linux: Yakuake
Whether you refer to it as a command line interface, console, or terminal, the terminal is one of the most important tools available on Linux. To that extent, it is important to always have rapid access to the terminal, and a little style has never hurt anyone. Yakuake brings the console to the forefront of your desktop with the press of a key, allowing you to quickly perform your tasks with ease.
Of course, one of the greatest advantages of Linux and Open Source is the flexibility to build an environment that best suits the end user. Some will argue that tiling window managers provide quicker access to the terminal, but to each their own. KDE has been my desktop of choice since the 2.0 days, so Yakuake fits the bill for a fast-access terminal emulator - and it can for you, too.