Unity - The multiplatform game creation tools for everyone.
LOVE 2D - Hi there! LÖVE is an *awesome* framework you can use to make 2D games in Lua.
Godot Engine - Feature-packed 2D and 3D open source game engine.
Pygame - Pygame is a set of Python modules designed for writing games.
Blender - Blender is the open source, cross platform suite of tools for 3D creation.
MonoGame - MonoGame is an open source implementation of the Microsoft XNA 4 Framework.