Roll20 - Roll20 is a suite of easy-to-use digital tools that expand pen-and-paper gameplay.
Spring Engine - Spring is a versatile 3D RTS game engine.
PlanarAlly - PlanarAlly is a web tool that adds virtual battlemaps with various extras to your D&D toolbox.
Unreal Engine - Unreal Engine 4 is a suite of integrated tools for game developers to design and build games, simulations, and visualizations.
Astral Tabletop - Create, host, and manage your tabletop role-playing games — online or in person
Lips of Suna - Lips of Suna is a tongue-in-cheek action RPG.