Fluxbox

Henrik Kinnunen started from Blackbox 0.61 and kept what people liked about it: a root menu on right-click, a slim toolbar and shareable style files. The new idea was tabs — several windows could be grouped under one title bar and flipped between, much like a browser, years before browsers made that the norm.

From Window Maker it borrowed the "slit", a strip where small dockapps such as clocks and CPU meters could be parked. Keyboard shortcuts lived in a simple keys file. Through the 2000s Fluxbox was the stock answer to "what should I run on this old laptop?", and it lasted a long time in live CDs that had to boot on anything.