PixiEditor is a free, open source 2D graphics editor that you can use to create video game sprites, animations, pixel art, painting, and even vector art.
Graphite is a free, lightweight open source 2D graphics editor and animation tool that features a procedural, node-based compositor, in addition to traditional layer-based workflows.
Inkscape is a free and open source vector art editor that uses Scalable Vector Graphics (SVG), allowing your artwork to be scaled to any size without losing quality.
MediBang Paint is a versatile and free digital painting and manga creation software available on multiple platforms, including Windows, Mac, iPad, iPhone, and Android.
GIMP is a free and open source raster graphics editor used for a variety of graphics editing tasks such as photo retouching, image composition, image authoring, and even drawing and painting.
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.