Game engine and multimedia framework and display server.
Ranked in these QuestionsQuestion Ranking
Pro Nice API for custom Window Managers
A pro- for programmers, but it is much easier to write a Window Manager for Arcan that it is for Xorg or any of the other options.
Pro Tons of features
So many things that can be done - video recording, streaming, clipboard managers, crash recovery, live window manager swapping, ... the list is endless.
Pro VR support
Pro Very customizable
Con Difficult configuration
To work it requires configured Lua files, command line options, environment variables.