Phaser is a free and fast 2D game framework for making HTML5 games
Easy to use Python library for creating 2D arcade games
Creative cellular automata browser game
Godot game template and component-based framework
A Phaser CE plugin that brings sloped tile collision handling
3D .NET engine for Windows, Linux, Mac
3D simulation library
Box2d Flash Alchemy Port + World Construction Kit
1st 3D game engine built in C# for .NET, Visual3D Engine's predecessor