Vi
Vi is undoubtedly the best editor in the world, at least IMHO, and it exists in multiple versions, the most popular of which is probably vim written for a multitude of platforms.
Via /. comes a pointer to an interview with Bill Joy, vi's original author.
The article points us to two other interesting stories here and here, both of which will be hard to understand for the younger generation. 
BTW, I have worked with vi over a 1200baud line; deduce my age, and this posting (as most of mine are) was written in vi.
Jan-Piet Mens / Mutt wrote on 15-Mar-07 at 9:17 pm
[...] mail, and most of the mail I send to Internet correspondents also originates in Mutt, written with this of course. Mutt is first when it comes to testing new systems, as it allows me to quickly and effectively see [...]
Jan-Piet Mens / Regular Expressions wrote on 26-Mar-07 at 9:35 am
[...] learn regular expressions? Because they are used in all good text editors, including such gems as Notepad2 for Windows, and because a lot of programs in Unix/Linux use [...]
Jan-Piet Mens / The OpenCD wrote on 14-Apr-07 at 10:26 am
[...] favorite small text editor for Windows (after vi of course) is also featured: Notepad2 is an indespensible replacement for the built–in [...]