Greenshot - Greenshot is a free and open source screenshot tool that allows annotation and highlighting using the built-in image editor.
OBS Studio - Free and open source software for video recording and live streaming for Mac, Windows and Linux.
Shutter - Shutter is a feature-rich screenshot program.
Screencast-O-Matic - Free version Records up to 15 minutes, premium is $15/year.
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
Droplr - Droplr is a tiny application that aims at helping people share things easier.