Unity - The multiplatform game creation tools for everyone.
Platforma - Wireframe library of layouts and UI elements
Godot Engine - Feature-packed 2D and 3D open source game engine.
Contra Wireframe Kit - Open source wireframe kit for design and prototyping 🚀
Blender - Blender is the open source, cross platform suite of tools for 3D creation.
Source Wireframe Kit - Library of 537 blocks for desktop and mobile prototyping