Design Oriented Topic Wheel — A huge glossary on gamedev topics made in an interesting interactive way. Make sure to disable DarkReader or other "dark theme" extensions in your browser to actually see the definitions!
Figma — though it is a prototyping and UI design tool, it has powerful capabilities for vector and is great for illustrations and cartoony game sprites. CoMiGo's go-to graphics tool. Works in a browser and as a desktop app.
Aseprite on GitHub — yes, it is a paid app, but did you know you can compile it by yourself for free, and that it is absolutely legal? If you don't want or can't build it by yourself, check LibreSprite, a fork of Aseprite.
Piskel — a free online pixel art editor. Supports both animations and layers.