Unreal Engine - Unreal Engine 4 is a suite of integrated tools for game developers to design and build games, simulations, and visualizations.
FreeCAD - An open-source parametric 3D modeler
Unity - The multiplatform game creation tools for everyone.
LibreCAD - An open source 2D CAD application for Windows, Apple and Linux.
AndEngine - AndEngine is a free android 2D OpenGL game engine.
SketchUp - 3D for Everyone