By far the best, lightest, and cheapest visual design tool.
It is straightforward and powerful, and has lots of tutorials and learning resources straight from the developer's siteCons:
It has maybe too many windows for all its tools
Adobe photoshop is a great software but has become, over the years, a huge dinosaur. Obviously it has tons of feature, but in the real world of developers ho needs to create and change assets, pixelmator comes to the rescue!