CotEditor is an open-sourced, Cocoa-based plain-text editor for OS X. It supports syntax highlighting, powerful find-and-replace with OniGmo (regular expression engine), and other small goodies for coding. It can handle also CJK languages well.
Colorize more than 40 pre-installed major languages like HTML, PHP, Python, Ruby or Markdown. You can also create your own settings.
Super powerful find and replace using OniGmo regular expression engine.
There are no complex setting files that require geek knowledge. You can access all your settings including syntax definitions and themes from a normal preferences window.