BBEdit, Yojimbo, and TextWrangler (all BareBones software) have some pretty dedicated followers esp. in the mac blogging world. I think BBEdit was my first text editor back when I got a demo with a copy of MacWorld years ago.
I used and loved it for years, but when MobileMe died and Yojimbo languished I moved on to Evernote, for better or worse.
I use it as a scratchpad for ideas I want to write up, as a stash of notes and to-dos, a bookmark organizer and other stuff.