Greenshot - Greenshot is a free and open source screenshot tool that allows annotation and highlighting using the built-in image editor.
TeamViewer - TeamViewer lets you establish a connection to any PC or server within just a few seconds.
Shutter - Shutter is a feature-rich screenshot program.
AnyDesk - AnyDesk is the world's most comfortable remote desktop application. Access all your programs, documents and files from anywhere, without having to entrust your data to a cloud service.
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
join.me - Instant screen sharing. Instant Aha!