Pretty much any Unix system will have vi installed, even if they don't have any other editor. Regardless, it's a good idea to at least learn the basics of Emacs and Vi. For those who just want to use a basic editor or feel intimidated by Emacs and Vi there's also UW's Pico and its opensource clone GNU Nano. These are powerful programmers editors, which have tons of functionality and scriptability at the cost of a steep learning curve. The main divide is between whether to use Emacs or Vi.
Among Unix users there is great debate about the best text editor to use.
