Unity - The multiplatform game creation tools for everyone.
Corona SDK - Cross-platform mobile app development.
Godot Engine - Feature-packed 2D and 3D open source game engine.
BuildBox - Buildbox is a new video game maker that is extremely easy to use.
Blender - Blender is the open source, cross platform suite of tools for 3D creation.
Cocos2d-x - Cocos2d-x is an open-source and cross platform open source free 2D game engine for mobile game development known for its speed, stability, and easy of use