Textmate, Firebug, Chrome & Safari's web inspector, Sequel Pro (for MySQL), Gitx, github.com, and Terminal.
Currently while developing a Rails app I'm using Notepad++ on my provided XP machine. And normally Pico when SSH'd in, making quick updates.
Emacs and firebug.
Textmate, Firebug, Chrome & Safari's web inspector, Sequel Pro (for MySQL), Gitx, github.com, and Terminal.