Terraria - Dig, Fight, Build! The very world is at your fingertips as you fight for survival, fortune, and glory.
Unity - The multiplatform game creation tools for everyone.
Starbound - This action-adventure platformer throws you into a procedurally generated galaxy where you can make your mark.
Struckd - 3D Game Creator - Struckd is the next-generation gaming platform for user created content where people of all ages...
Dig or Die - Dig or Die is a sandbox action/strategy game; explore, fight, craft, and build your defenses!
Reality Factory - Reality Factory is a free suite of game development tools for building 3D games.