Byword is a simple text and Markdown editor that provides a minimal environment focused on text and not options. It provides some nice options for writers who enjoy plain text and Markdown such as full-screen mode and automatic line and paragraph focus modes. The developer also maintains an IOS version so you can work on files saved to the cloud.
For other Markdown editors, see here.
Pro Exemplary Markdown support
Byword de-emphasizes the syntax itself, while emphasizing its effects. It appropriately adds style, like italic and bold, to text that's designated by markdown and dims the syntax so it does not getting in the way of comprehension. Additionally, there are commonly used hotkeys (⌘b, ⌘i, etc) that can be used to apply style without having to know the syntax or having to type it out each time.