Picpick

Picpick is a great tool for taking screen capture of anything at any specific region on your PC. It can also be used for image editing, which comes with many advanced design accessories and features. It is free for your personal use, however you need to buy for professional use.

A full-featured screen capture tool, Intuitive image editor, color picker, color palette, pixel-ruler, protractor, crosshair, whiteboard and more.
Source

Salient features:

• Image Editor
• Add Effects to images
• Share to the Cloud and Social media
• Multiple design tools

To know about more of its features head over to this link.