Things I’ve done relatively recently
OpenRW is an open source engine written in C++ intended to be compatible with game data for the 2001 video game Grand Theft Auto III. Currently it has support for executing game script, rigid body dynamics, character interactions and hard-coded gameplay elements.
Source code is available via github
Projects that were sunset a long time ago.
Simufarm was a 3D simulation title intended to compete with SimTractor. Originally using irrlicht as a basis, the project moved to use Ogre3D. It integrated PhysX for vehicle and rigid body dynamics, as well as collision detection for planting and harvesting crops.