Unity - The multiplatform game creation tools for everyone.
3D Hubs - Airbnb for 3D printing
Unreal Engine - Unreal Engine 4 is a suite of integrated tools for game developers to design and build games, simulations, and visualizations.
Muglaunch.com - Design and sell print on demand products easily @ Muglaunch
Blender - Blender is the open source, cross platform suite of tools for 3D creation.
Zazzy - Design and sell your own 3D printed jewelry