FlatRedBall - Cross-platofrm 2D game engine using C#, focused on developer productivity, transparency, scalability, and ease of use.
Unity - The multiplatform game creation tools for everyone.
MonoGame - MonoGame is an open source implementation of the Microsoft XNA 4 Framework.
Godot Engine - Feature-packed 2D and 3D open source game engine.
Blender - Blender is the open source, cross platform suite of tools for 3D creation.
Wave Financial - Award-winning financial software designed for entrepreneurs.