How do I log into bash shell only?

view story

http://askubuntu.com – On my home desktop I want to use Ubuntu Unity sometimes and just the bash shell (without any GUI) other times. Is it possible to set up a login option where I can choose between using the Unity GUI or just the shell? For example, on the Ubuntu login screen I can choose among Unity, Gnome Shell, XFCE, etc. An option there for just the Bash shell command line would be ideal. I'm not trying to invite "why would you do that" debate here. I have my reasons. (HowTos)