Greenshot - Greenshot is a free and open source screenshot tool that allows annotation and highlighting using the built-in image editor.

Placeit - Generate realistic product shots in seconds

Shutter - Shutter is a feature-rich screenshot program.

Screenshot.rocks - Create beautiful browser mockups from your screenshots

Snipping Tool - Use Snipping Tool to capture a screen shot, or snip, of any object on your screen, and then annotate, save, or share the image

Pika App - A free tool to quickly generate beautiful browser screenshots. You can capture screenshot from website, add browser frames, 3d tilt-effect, background colors to screenshots and more