flwm

Bill Spitzak wrote the FLTK toolkit, the Fast Light Toolkit, at the effects studio Digital Domain in the late 1990s for the compositing program Nuke, to get away from Motif. flwm followed soon after as proof that it was enough to build an entire window manager on. The model was Chris Cannam's wm2: the title bar is a narrow strip down the left edge of the window with the text rotated ninety degrees, so it costs width rather than height on screens where height was what ran out. No icon row, no buttons to speak of; a menu on the root window lists open windows and desktops.

The program is a few tens of kilobytes and is up before the terminal has drawn. That gave it a niche FVWM and Enlightenment never aimed at: the minimal distributions. Tiny Core Linux picked flwm as its default, in the flwm_topside variant with the title bar on top for anyone unwilling to tilt their head. Since then flwm has led the quiet life that is a finished program's privilege: no releases to wait for, nothing to break.