Posterist - Create beautiful photo collages in minutes on your Mac
Unity - The multiplatform game creation tools for everyone.
FotoJet - Free Online Graphic Designer | Collage Maker | Photo Editor
Godot Engine - Feature-packed 2D and 3D open source game engine.
QwikBanners - Get your display network campaign going in few clicks, generate all sizes in few seconds, no coding or design skills required
Blender - Blender is the open source, cross platform suite of tools for 3D creation.