Carambis ScreenShooter 

Carambis ScreenShooter is a neat and handy application that lets you quickly take screenshots and share them online or save them to local image files.

This handy tool is very easy to use thanks to the fact that it supports customizable hotkeys which let you quickly capture a specific area of the desktop, a window, or the full screen. It can be easily accessed from its tray menu icon. After taking a screenshot, a simple image editing window allows you to add rectangles, lines, circles, or arrows to the captured image (which helps you annotate and highlight areas of it), crop it, blur it, or even add a text to it. Then the captured image can be saved locally as a PNG file or shared online using either the Carambis Cloud storage service or via e-mail. Even saving to a FTP location is possible.

As you can see, this screenshot taking tool is both simple and relatively feature-rich. The only thing that I'd add to it would be the possibility to save in multiple image formats, besides PNG. Anyway, since it's also free, Carambis ScreenShooter gets my appreciation despite the small aforementioned flaw.