Mockuuups Studio - Fast and easy way to create product mockups on macOS, Windows and Linux.
Greenshot - Greenshot is a free and open source screenshot tool that allows annotation and highlighting using the built-in image editor.
Smartmockups - Create stunning product mockups, easily and online.
Shutter - Shutter is a feature-rich screenshot program.
MockMagic - A free, easy-to-use device mockup generator
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