Cacoo is recommended for project managers, designers, engineers, educators, and remote teams who require a collaborative environment to brainstorm, visualize ideas, and manage projects through diagrammatic representations.
Godot Engine - Feature-packed 2D and 3D open source game engine.
LucidChart - LucidChart is the missing link in online productivity suites. LucidChart allows users to create, collaborate on, and publish attractive flowcharts and other diagrams from a web browser.
Unity - The multiplatform game creation tools for everyone.
draw.io - Online diagramming application
Unreal Engine - Unreal Engine 4 is a suite of integrated tools for game developers to design and build games, simulations, and visualizations.
Gliffy - Gliffy is a powerful HTML5 online diagram maker. Create a flow chart, network diagram, UML diagram, organizational chart or wireframe with ease.