Open source reimplementation of GTA San Andreas game engine in Unity
2D Game Engine
Modern 3D engine and IDE written using C# and C++.
Vivid Engine 2 is an open source 3D Engine coded using C# and C++.
Launch apps/games on your HDMI-connected TV (or any other display)
A game maker written in C# and FreeBASIC
1st 3D game engine built in C# for .NET, Visual3D Engine's predecessor
Final Fantasy XI Scripting Bots Automation