Godot Engine - Feature-packed 2D and 3D open source game engine.
Spine - Spine is 2D animation software designed specifically for software and game development.
Unreal Engine - Unreal Engine 4 is a suite of integrated tools for game developers to design and build games, simulations, and visualizations.
Synfig Studio - Just another WordPress site
Unity - The multiplatform game creation tools for everyone.
Unity 2D - Unity 2D is a powerful and feature-rich game design solution built from the ground up to fulfill every basic and advanced need of the developer.