Vim. I think it can be in the list as well. It takes a long time to properly learn. But one hours is defiantly enough to get to know the main Vim bindings, to be as productive as in other editors. In the end it makes you super productive.
Nothing has influenced my use of computers as much as Vim, and I'm really glad this tool exists. It makes editing text a great experience, and has a couple feature you can't find anywhere else(not even Emacs offers such a flexible, intuitive keybinding functionality or reliable, quirk-free controls).