Epic Pen - A windows tool for drawing over your desktop and applications
Droplr - Droplr is a tiny application that aims at helping people share things easier.
Gromit-MPX - Create annotations by directly drawing on your screen.
ConnectWise Control - ConnectWise Control is a mobile app that allows you to instantly connect with another system from anywhere with a connection to the internet. The software not only comes in a mobile app, but it has a desktop version as well for complete coverage.
OBS Studio - Free and open source software for video recording and live streaming for Mac, Windows and Linux.
gInk - An on-screen on-screen annotation software for Windows.