Erato is a beautiful and simple Markdown editor for your Mac. It is fast, extremely easy to use and gets out of your way.
With UberWriter it’s simple to write beautiful documents in Markdown.
An absolutely stunning and fully-featured text editor that works in Windows, OS X and Linux. (via Friendly Bit)
A good Mac rich text editor. My favourite feature? Built-in statistics showing how often different words are used in a given document. Really useful for improving one’s writing.
$21/€15, with free updates for life.