Godot Engine - Feature-packed 2D and 3D open source game engine.
Friv - A safe place to play the very best free games!
GDevelop - GDevelop is an open-source game making software designed to be used by everyone.
Armor Games - Play free online games at Armor Games! We're the best online games website, featuring shooting games, puzzle games, strategy games, war games, and much more...
Unreal Engine - Unreal Engine 4 is a suite of integrated tools for game developers to design and build games, simulations, and visualizations.
Kongregate - Kongregate has free games that you can play online. Choose from thousands of free flash games.