DrawPile - Drawpile is a drawing program that lets you share the canvas with other users in real time.
Sketch - Professional digital design for Mac.
PaintTool SAI - Learn to draw in different ways.
Inkscape - Inkscape is a free, open source professional vector graphics editor for Windows, Mac OS X and Linux.
Excalidraw - Excalidraw is a whiteboard tool that lets you easily sketch diagrams that have a hand-drawn feel to them.
Adobe Photoshop - Adobe Photoshop is a webtop application for editing images and photos online.