SublimeText 3 is the text editor: slim, fast, neat and extendable via package management system.
Git
GitGutter
Bracket Highlighter
Markdown Preview
Better CoffeeScript
SideBarEnhancements
AdvancedNewFile
CapybaraSnippets
ERBSnippets
Sass
Ruby Hash Converter
RubyToggleString
RSpec
RailsCasts Colour Scheme
Railscasts Extended
Tomorrow Color Schemes
Predawn