Become a Screenshot Master with Shutter
Shutter is a free and open-source screenshot program that offers advanced capturing, sharing and editing abilities. It stands out for its feature richness and editing power that will save you time jumping from one application to the other, and adds professional look, or artistic style to your screenshots!
You can do 5 different kinds of capturing. You can capture your desktop, a specific area, a single window, a menu or tooltip and a website. This covers every possible capturing need so I think there is no point in analyzing it further.