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.