Lightshot is the fastest way to take a customizable screenshot. Simple interface, nothing useless and light weight.

Gyazo is an open source screenshot program for Windows, Mac OS X and Linux.

Grabilla is a software that takes a screenshot of the user's computer screen and uploads it to the Web, FTP, computer or copy to clipboard.

Skitch makes taking, annotating, and sharing screenshots or images is as fun as it is simple.

DuckLink Screen Capture is a screen capture software.