RenderDoc is a stand-alone graphics debugging tool
Realtime raytracer using SIMD on ARM, MIPS, PPC and x86
Full featured MUD server with all the trimmings.
Explore and dissect a complete brain model in VR
Open-source CUDA/OpenCL speed of light ray-tracer
Pear3DEngine is a modern and modular 3D development framework
1st 3D game engine built in C# for .NET, Visual3D Engine's predecessor