It's sad that Acme hasn't been mentioned at all. While its mouse-oriented nature is a little strange coming from Vim, there are some very awesome ideas in it. For one: It lets you write plugins in anything you like. This is because all aspects of the editor are exposed as a filesystem a la /proc. Need to create a new window with some custom contents? Create a new file. Other awesome ideas: The text in that custom window can be actions because any text can invoke commands by using another mouse button.
Russ Cox has a great video tour of Acme's features here: http://www.youtube.com/watch?v=dP1xVpMPn8M