It's a text editor that I first used on plan9. I tried it out in the 90s, and I didn't "get it" back then, but I kind of liked Sam.
http://en.wikipedia.org/wiki/Sam_%28text_editor%29
I'm a self-described operating system junkie. At home, I've got WinXP, Win7, OpenBSD, OS X, Haiku (BeOS), FreeBSD, Solaris, AIX, and a few Linux flavors running. Yes, all at once. Maybe I should try plan9 again in a VM.