Fluxbox - Fluxbox is a window manager for X that was based on the Blackbox 0.61.1 code.
Xfce - Xfce is a lightweight desktop environment for UNIX-like operating systems. It aims to be fast and low on system resources, while still being visually appealing and user friendly.
IceWM - icewm home page . Bug Tracking. If you have a patch, a bug report or a feature request to submit, please do so at the icewm project page at SourceForge.
LXDE - Why will you like it? Less resource needs. You can use it on your less-pricey embedded board or salvaged computer. Component-based design. Don't want something in LXDE, or you don't want to use LXDE but only part of it?
KWin - KWin is a window manager for the X Window System, and is in the process of becoming a Wayland...
KDE Plasma Desktop - Plasma Workspaces is the umbrella term for all graphical environments provided by KDE.