Greenshot - Greenshot is a free and open source screenshot tool that allows annotation and highlighting using the built-in image editor.
wisaw - What I Saw Today (cool things) -- Minimalistic Anonymous Photo Sharing
ShareX - ShareX is a free and open source program that lets you capture or record any area of your screen...
Szoter - Szoter is easy to use, free, online image annotation tool. Annotate, draw and highlight any image.
LightShot - The fastest way to take a customizable screenshot.
WallaMe - Hide messages in the real world using augmented reality