Doorcs is a shell created by Kerm Martian and written in assembly.
This is the biggest shell and it provides a complete graphical interface (you can even use a mouse).
It can be used to play sound, or launch various type of application/programs (as other shells does).
You can also use the graphical lib to do your own programs.
More information here :
http://dcs.cemetech.net/index.php/Main_Page