Clearly the best OpenSource editor. If people say it's too complex etc; that's partially true but it's worth learning it. Really, really powerful and you can script it in many languages including ruby and python.
Here some links if you're new to Vim or want to find out something new:
The only competition here is EMACS. I prefer vim because it's more lightweight and installed practically everywhere. It takes an effort to learn all the commands but once you're there, the coding efficiency goes to 500 % and you don't ever want to go back. Truly the ultimate editor.
The editor I can use everywhere: Windows, Linux, AIX, HP-UX. Either in a graphic environment or in a text terminal. Using the same configuration and plugins that I have accumulated for years from hosts to hosts.
I'm everywhere at home once I have Vim running! This is the swiss knife for a software contractor like me.