Alien Swarm - Alien Swarm is a F2P, Co-op, Alien, Top-down Shooter, Single and Multiplayer video game developed and published by Valve Corporation.
Unity - The multiplatform game creation tools for everyone.
Crimsonland - Crimsonland.com - a top-down shooter with a touch of RPG: gain XP, choose perks, unlock weapons, and blast your way through aliens, zombies, and lizard men. Coming soon to Steam and PS4!
Godot Engine - Feature-packed 2D and 3D open source game engine.
Alien Shooter 2: Reloaded - Alien Shooter 2: Reloaded combines the elements of Role-playing, Top-down, Action, and Shooter.
Blender - Blender is the open source, cross platform suite of tools for 3D creation.