The editor I prefer is vim, I have used it in OpenBSD adJ (my prefered OS), Linux and even Windows.
Some time ago I used emacs and eventually I have to use mg that is a stripped version. I have also used pico in Linux and nano in OpenBSD. All of them can be used from a terminal. For newcommers to Linux and OpenBSD adJ, for quick edits I recommend gedit an xfw respectively.
In a course I organized in P2PU in spanish we had a week about some of these text editors: