Game engine supporting many 3D/2D formats and graphic effects
GemRB is a portable open-source implementation of the Infinity Engine
A .NET ascii/ansi console engine written in C# for MonoGame and XNA
Go bindings for raylib, a simple and easy-to-use library
RTSish Game Engine
Play Fighting Fantasy fan stories on this simple engine
A modern, cross-platform Quake game engine based on FitzQuake.
An isometric arcade-style game of skill, puzzles and exploration
Orx: Data-Driven Game Engine
Amateur 3D Game Engine
C++ lightweight cross-platform game engine
Injectable LUA scripting system, SDK generator, live property editor
Vivid3D is an open-source 3D engine with powerful 2D UI.
Spring is a free RTS engine developed for Windows, Linux and Mac OS X.
Vivid is a modern C++ 3D engine using OpenGL4+
Go 3D Game Engine
DOOM / Heretic / Hexen source port with enhanced graphics and UI
2D Game Engine
mGSTEP port of the Cube game engine