Blender (App)
Blender is an all-in-one free and open-source 3D modeling program that allows you to model, sculpt, rig, animate, run physics simulations, render, composite, and even draw and paint all in one application.
FireAlpaca (App)
FireAlpaca is a free digital painting software designed for both Windows and Mac users, featuring regularly updated brushes, comic panels, animation tools, mesh transform, 3D perspective tool, and more.
Krita (App)
Krita is a free open source digital drawing and painting app with all the features you need to start making professional-grade illustrations.