These are all onboard from day one. OK, TextEdit defaults to RTF but just select Format->PlainText and you're there. Emacs and vi are available from terminal, TextEdit is in your apps folder. If you like, you can install the dev tools and use ProjectBuilder but its kind of a LSE and might be annoying for certain kinds of files.
I generally use vi for small things, TextEdit for more involved editing/html page stuff, and PB for source code.
My officemate is an all emacs all the time kind of guy.