Terraria - Dig, Fight, Build! The very world is at your fingertips as you fight for survival, fortune, and glory.
Reality Factory - Reality Factory is a free suite of game development tools for building 3D games.
Starbound - This action-adventure platformer throws you into a procedurally generated galaxy where you can make your mark.
CraftStudio - CraftStudio lets you craft games from scratch in real-time over the Internet.
Deepworld - Deepworld is a massively-multiplayer 2D crafting adventure game.
Limon Engine - Limon is a multi platform 3D game engine mainly focusing on first person games.