Jul 15th, 2014 Krita, a complete, free digital painting suite
The interface style is influenced by Adobe products, as well as by Corel digital drawing tools, so anyone who has used Photoshop before can quickly get the hang of it.
It includes a lot of different brush types and effects, the ability to work with layers, support for the most widely used image formats, palettes, cropping, and vector manipulation, as well as different retouching tools.
The best thing about it, though, is that it's an open source application under GNU license. This makes it a great alternative to Gimp, the most popular open source image editor by far.