What's that I hear you say? You loathe GUI's? You really, really hate desktops and consider them a necessary evil at best? Well, then, when you absolutely have no other choice but to leave your comfy console environment, you might consider TWM (stands for "Tab Window Manager").
Mind you, TWM was nothing more than one of the first desktops for the X window system ever created. It is more a starting point to build a complete window manager than it is a stand-alone system on it's own. It's not even actively developed anymore! TWM starts out as a blank blue screen on which you left-click to get the only menu. By default, that menu will have about five functions and an xterm. Whatever windows you open from there will have a dot on the top left to minimize them, a box on the top-right to resize them, and the title in the middle.
Believe it or not, any GUI program will run here, just like any other desktop. Yes, Firefox, Gimp, KDE panel, you name it! So if you, say, have a utility to change the desktop background, it will work here, too. This is surprising, because TWM was written in 1987 and doesn't look a minute younger. The development legend has it that the creator simply sat down at his Sun monochrome workstation and wrote it in vi in a single sitting so he'd have something nicer to look at...by 1987 standards.
If you're still reading, I might as well tell you about the upsides: never hangs or crashes, ever. Available wherever there's an X system, because it's bundled with X itself. Configurable from a single text file; there is actually quite a few things you can do, here, but it's never going to look like anything but TWM. Guaranteed to be the fastest desktop, period. Ideal for older system and servers. Will be your most productive environment ever, since there's nothing to do on it *but* work. With the right set of applications in the menu, it can be quite usable.
In fact, it would be almost usable on a general basis, if it only could support virtual desktops. But it can't, and it's the only desktop I'm covering here that can't. Many derivatives of TWM have added this, however.
Of course, I would tell newbies to stay away from it. However, I could recommend it be kept around for emergencies; it's saved my neck on occasions where my hardware configuration was hosed. It is also ideal for professional applications such as consoles and render farms and other limited-use scenarios.