Pixelmator

Pixelmator is one of the best graphic editor developed for Mac. It uses Core Image and OpenGL technologies that use the Mac's video card for image processing.

For those, who are constantly looking for "another Photoshop", Pixelmator is a great choice. It has a nice and uncluttered interface, it's very easy to learn and use and the effects rock! The only problem I've checked, so far,  is that many useful tools are missing, like shape-drawing tools.




Trial link:
http://www.pixelmator.com/try/