IceWM was amazing: fast, relatively configurable but very usable out of the box. The Motif window decorations looked real cool on screenshots as if I was running CDE. If memory serves, you could roll a window only to its title bar which is an old Mac OS9 feature that didn't carry to OS X.
AmiWM and WindowMaker also saw their usage but at the end of the day I always kept coming back to IceWM.
> If memory serves, you could roll a window only to its title bar which is an old Mac OS9 feature that didn't carry to OS X.
This behavior still exists with the “Stickies” application, itself an import from the pre OS X days!