CTFs as you need them
Game engine supporting many 3D/2D formats and graphic effects
PyCAPGE - Python Classic Adventure Point and Click Game Engine
Modern 3D engine and IDE written using C# and C++.
Asphyre is a cross-platform framework for Delphi and FreePascal.
Perl bindings to the Modern OpenGL API
3D .NET engine for Windows, Linux, Mac
Gorgon Game Engine (GGE) is a C++ game engine that handles many tasks.
Cross-platform C framework very compact libraries and tools.
Educational framework for OpenGLES, OpenCL and OpenAL
2D Game Engine, based on OpenGL and focused on Isometric Games
A graphics engine + toolkit.
Extremely simple joystick rumble / vibration library
Pear3DEngine is a modern and modular 3D development framework