mwm

For the true minimalist:

• ~40 LOC.
• No default keybindings (just edit the source).
• No title bars, no status bars, no buttons, no borders, no menus, etc.
• No mouse control.
• No virtual desktops.
• No configuration files.
• Absolutely adabptable to your needs.
• Includes just what is strictly needed.
• Not standards compliant (because, honestly, who gives a fuck?).
• All windows are full-screen, just one is visible at any given time.

mwm just loops through X key press events and lets you bind actions to key presses. It provides two macros: grab and K. Read the source for an example on how to use it (my own setup).

Dead simple.