Multi-platform Engine for Desktop, XBOX (UWP) and Mobile games
scene-oriented, flexible 3D engine (C++, Python, C#, Java)
2D game development library for Ruby and C++
Vivid is a modern C++ 3D engine using OpenGL4+
2D Game Engine
A 2D game engine and level editor
Cross-platform 2D and 3D game engine
A cross-platform 2D game engine
Real-time RPG for PC/tablet/phone; multiple quests and random dungeons
scriptable game engine with built-in support for 2D graphics and sound
The Atomic Game Engine is a multi-platform 2D and 3D engine
Open-source, cross-platform, C++ game engine for creating 2D/3D games
A generic 2D engine for any kind of game
2D physics engine for games
2D - 3D game engine
2D Game Engine, based on OpenGL and focused on Isometric Games
3D game engine for C and C++
WGFX 2D Game Engine