Acme is the reason I became interested in Plan9. Acme is Plan9's text editor. It is wild and powerful (much like a bison?). Acme is a text editor where the text is also the user interface. Here is the best example I've found of Acme in action.
It is a wee bit brain bending to get used to, but once you find your sea-legs with Acme you start to want the power it offers everywhere.
I typically use Acme through plan9port. Here I launch it with an alias,
alias acme='acme -f /usr/local/plan9/font/luc/unicode.8.font -a'
The -f flag launches acme with a larger than normal font (I like big fonts and cannot lie).
The -a flag makes it so that the current level of indentation is preserved when you move to a new line.