TikZ editor for Mac OS

I think TikZ-Editor is what you are searching for. It has a beautiful Mac-ish interface and the same features as tikzedt.

And just to complete the list – I used Latexian before, it also provides live preview and an even better interface. You can use Latexian for editing full LaTeX-Files, too.

Edit: As I just saw, there is no WYSIWYG-Editing in TikZ-Editor...

First of all I'd like to suggest you to take a look at this page: TikZ Resources. There is a list of tools that you can use to work with TikZ. It is must-have bookmark, full of resources, articles and examples.

I would suggest you to use this tool: TikZiT.

(I know an answer has already been accepted, but I can't pass over this editor)

Another very good editor is Latexit. Its main purpose is to write equations that can then be sent to other applications, but it has many other uses. I use it to draw my tikz pictures. It is easy to use. In addition it has a library, where you can store all of your art and reuse it later. Once your picture is complete you can paste the code into your TeX document, or save it in many different formats.