Vim

VIM. Vi IMproved. noun

For a comprehensive run-down on vim's many features and how to use them, go here.

Vim is one of the best editors around and it possesses a wide range of powerful features which give the user complete control over the program. With this power also comes complexity, vim can take a few minutes of pratice to get used to. (check out the tutorial) Once you have learnt the basics a wide vista of potential opens up.