I like TikzEdt, which provides a graphical interface to edit tikz pictures. Although it is not as powerful as other graphics tools (Photoshop, Inkscape,...), for me it is the perfect combination of both worlds: you still take advantage of the tikz magic (code-based, LateX integration, ...) but also directly see what the image will look like without manually iterating through the edit - compile cycle.
(Sadly, the last update to the project was 4 years ago, so the original maintainer seems to have lost interest. But, nonetheless, it is open source.)
