Godot Engine - Feature-packed 2D and 3D open source game engine.
Synfig Studio - Just another WordPress site
Unreal Engine - Unreal Engine 4 is a suite of integrated tools for game developers to design and build games, simulations, and visualizations.
Creature - Creature 2D Skeletal and Mesh Animation Tool
Unity - The multiplatform game creation tools for everyone.
Live2D Cubism - Live2D is the world's first drawing technology to enable 3D rendering of 2D images.