HeroEngine is 3D game Engine. It is a platform for all-in-one development to make and operate online games. It is written in C++, C# and HeroScript Language (HSL) and used to develop games for the platform of Microsoft Windows. HeroEngine was developed by Simutronics Corporation for the game Hero’s Journey; however the game was never released.

Gold Source also named as GoldSrc is a powerful 3D game engine of its time. It is written in C/C++ and mainly used for modding (modifications in code) with its mod development tools. The engine is used to develop games for windows, Playstation 2, Mac OS, Linux and Dreamcast.

GoldBox is a Propriety Game Engine developed by SSI (Strategic Simulation Inc.) in 1988. This engine is written in C/C++ but its initial version was written in Assembly and PASCAL. It developed games for the platforms of Apple II, Apple Macintosh, Amiga, Commodore 64, Atari ST, DOS, NES, NEC PC-9800, and Sega Genesis.

Godot is a cross platform free and open source game engine with MIT (a light license) licensing. It is written in C++ and C# and used to develop 2D and 3D games. The development environment runs on Windows, MacOS and Linux and develops games for platforms like windows, Linux, macOS, iOS, Android, HTML5, WebAssembly and Xbox One.

Gameplay 3D is a Cross-platform game engine used to develop 2D and 3D games. Written in C++, this is used to develop games for Windows, Android, Linux, Blackberry, iOS and MacOSX. The game engine supports Visual Studio, Xcode, CMake, Qt Creator and Android NDK platforms to develop and build the platform.

G3D Innovation Engine is a fully featured, cross platform game engine. This is a 3D engine written in C/C++. It is a commercial-grade, open source engine for different platforms i.e. Windows, Linus and Mac OS. The engine is licensed under BSD-2 license and mainly used for teaching purpose.

Gambryo is a cross-platform game engine written in C++. It is a suit of several C++ libraries, plug-ins and run-time libraries. The engine supports several platforms like Windows, Android, Mac, Linux, iOS, Wii, Wii Ware, Xbox, Xbox 360, Xbox One, PS X, PS 2, PSP, PS3 and PS4.

Frostbite is a powerful game engine developed by DICE Company in 2008. This Game Engine is written in C++ and C#. It develops games for PS3, PS4, Xbox 360 and Xbox one. It exclusively develops games for electronic Arts and specializes for FPS (First Person Shooter) games.

Exult is a FOSS (Free and Open Source Software) game Engine. It is written in C++ and runs on Mac, Windows and Linux. Exult was developed in 2004 to recreate a massive hit game of 1990’s called Ultima VII. It is created for the revival of Ultima VII (The Black Gate) and Ultima VII part2 (Serpent Isle) on modern PCs.

The word Esenthel is made by combining two words i.e. Essential and Essence. It is an open source game engine for developing commercial and noncommercial games (it is not Free, there are some limitations, i.e. its code cannot be used to create/improve other game engines.). It is written in C++ and is very easy to use. It uses very clean APIs. It is in development since 2000.