Greenshot - Greenshot is a free and open source screenshot tool that allows annotation and highlighting using the built-in image editor.
Annotable - Ultimate image annotation & markup tool
Swiftdrop - Swiftdrop is a super simple cloud sharing app for Mac.
Weava - Workspace to highlight, organize & collaborate on your research articles.
ScreenTray - A better way to capture, annotate and share screenshots
Airsketch - Simple screenshots + annotations for Mac 🖥️