I am missing RCS in the list...

So do I.
It's RCS and RCS is the rcs I use most of the time.
Typing documentation into a KwikiWiki using RCS is most of my using revision control.
Not counting when I use CVS, I use that for the code, but still a lot less than simple RCS... heck, I wanted to say that I would prefer to use Subversion, so that's my prefered rcs although I hardly ever use it.

Cheers, Sören