All-in-one program for creating 2D scrolling games. Compile your games into stand-alone .NET executables or customizable C# source code. The IDE and framework are build on OpenTK, which wraps OpenGL, so generated games can be cross-platform.
D2D Map Editor enables the rapid creation of tile based map grids. It’s easy to learn and can be used by programmers and non-programmers alike. The maps generated can be deployed in games and applications developed in C++, C#, ActionScript and XML.
1st 3D game engine built in C# for .NET, Visual3D Engine's predecessor
The first 3D game engine built in C# for .NET, predecessor to the Visual3D Game Engine (https://www.poweraccess.net/visual3d-game-engine), an All-in-One Game Development Tool for Next-Gen 3D Games, MMOs, Simulations and Virtual Worlds powered by Microsoft XNA.
OpenTheme is an XML based GUI toolkit with a set of foundation class and WYSIWYG editor. Although it's originally designed for full screen GUI, it is also good for Windowed user interface, with full localization support and arbitary look-and-feel.