Blitz3D - Create 2D and 3D Games for Windows.
Godot Engine - Feature-packed 2D and 3D open source game engine.
BlitzPlus - Create 2D Games for Windows.
GDevelop - GDevelop is an open-source game making software designed to be used by everyone.
Monkey 2 - An easy to use, cross platform, games oriented programming language
MonoGame - MonoGame is an open source implementation of the Microsoft XNA 4 Framework.