under debian even if you install some form of desktop such as MATE Gnome2 – /usr/bin/xinit is NOT installed.
not needed i guess.
so i you want to enjoy the most minimal and RAM saving GUI in the world with the famous „cross-hair“ you go:
apt-get install xinit xterm; # install xinit and xterm binary
init 3; # go into no gui mode
xinit; # start the thing
exit; # end xinit