CryENGINE!

Godot is a fully featured, open source, MIT licensed game engine. It focuses on having great tools, and a visual oriented workflow that can export to PC, Mobile and Web platforms. It is a cross-platform 2D and 3D game engine and game development IDE.

Unreal Engine is a professional suite of tools and technologies used for building high-quality games across a range of platforms. Unreal Engine’s rendering architecture enables developers to achieve stunning visuals and also scale elegantly to lower-end systems.

GDevelop is an open source game creation software, allowing to make games for the web (HTML5) or for Windows and Linux. No programming or coding skill is required! It is easy to use and powerful enough for advanced users.

Polycode's core is written in C++ and currently runs on Mac, Windows and Linux with iOS and Android support planned in the future. All platform-specific functionality is abstracted into a cross-platform core and implemented natively on each platform, so the same C++ code will compile on each supported platform out of the box.

Torque 3D is a easy-to-use game creation platform. Architected from the ground up for maximum flexibility and performance across a wide range of hardware and built upon the Frontline award-winning Torque Game Engine Advanced, Torque 3D comes equipped with a full suite of tools and APIs to get your game to the finish line, no matter what your goals. Add publishing paths to PC, Mac, Xbox 360, Wii, iPhone, and the web, and you have the power to distribute games almost everywhere they are played.

Superpowers is an HTML5 development environment for making 2D and 3D games.It can be extended with plugins and lets you collaborate in real-time.

Urho3D is a lightweight, cross-platform rendering and game engine implemented in C++ and released under the MIT license. Greatly inspired by OGRE and Horde3D.

Wick is a free Flash-like browser-based toolkit for creating small interactive things for the Internet. With Wick, you can create games, animations, and everything in between. Your creations can run on any device with a web browser - that means mobile too. And since Wick lives in the browser, you don't have to download any extra software to use it!

An open-source 3D/2D game engine for ObjectPascal.

Platinum Arts Sandbox Free 3D Game Maker is an open source free game maker, free RPG Maker, free sidescroller maker, free Machinima creator, and game design tool that makes it easy for kids and adults to create video games, maps and worlds.

Adventure Game Studio provides the tools to make your own adventure, for free! Bring your story and artwork and slot it in, and let AGS do the rest.

Amazon Lumberyard is a free, cross-platform, 3D game engine for you to create the highest-quality games, connect your games to the vast compute and storage of the AWS Cloud, and engage fans on Twitch.By starting game projects with Lumberyard, you can spend more of your time creating great gameplay and building communities of fans, and less time on the undifferentiated heavy lifting of building a game engine and managing server infrastructure.

Xenko is an open-source C# game engine designed for the future of gaming. It comes with a full toolchain and is especially well suited to create realistic games but allows you much more!The Xenko effort is proudly supported by Silicon Studio Corp., a 16 years old established technology and services company of 300+ employees, dedicated to driving entertainment forward. Silicon Studio develops world-class products to help developers maximize the potential of leading-edge digital media technology.

Phaser is a fun, free and fast 2D game framework for making HTML5 games for desktop and mobile web browsers, supporting Canvas and WebGL rendering.