These two low-cost apps don't report unique words however, they work great with Marked, which can help you visualize word repetition. Byword, also available on the App Store, is my personal favorite for writing in Markdown.iA Writer, available on the App Store, shows running word and character counts and is unique in that it estimates how long it takes someone to read your work.Word Counter isn't a text editor, but it can count your words, report word frequency, and provide readability statistics.Text Wrangler, by Barebones Software, is a free text editor that should be able to do what you ask and much more.I can think of several possible solutions at all price points to help you tally up your words.
