Common Lisp.
If you're tired of flipping through themes like channel-surfing, and going
from one perfect-except-for-just-one-thing window manager to another
even-more-broken-in-some-other-way then perhaps Stumpwm can help.
Stumpwm attempts to be customizable yet visually minimal. There are no window
decorations, no icons, and no buttons. It does have various hooks to attach
your personal customizations, and variables to tweak.
* Hack the good hack.
* Debug your good hack.
* Customize your window manager.
While it's running. That's right. With a 100% Common Lisp window manager
there's no stopping the hacks. Just re-eval and GO!
WWW: http://www.nongnu.org/stumpwm/