Examples of procedural geometry for Unity3D C#
2D Game Engine
Free and Open Game Programming Language for Windows and GNU/Linux
Build Cross-platform Applications
Asphyre is a cross-platform framework for Delphi and FreePascal.
3D .NET engine for Windows, Linux, Mac
Cross platform Game Creation Software
The classic intelligent role playing game
Cross-platform 2D game engine
Delphi-like IDE for cross-platform game development
Make games with Lego-like building blocks