Epic Pen - A windows tool for drawing over your desktop and applications
Krita - Krita is a professional FREE and open source painting program. It is made by artists that want to seaffordable art tools for everyone. Concept art. texture and matte painters, illustrations and comics.
Gromit-MPX - Create annotations by directly drawing on your screen.
gInk - An on-screen on-screen annotation software for Windows.
OBS Studio - Free and open source software for video recording and live streaming for Mac, Windows and Linux.
PaintTool SAI - Learn to draw in different ways.