NiL is a modular multi-purpose gaming engine including a multiplayer worm game a little like quake, except it's 2d and a little like worms except it's realtime.
Leadwerks Arena is an open source first-person/third-person arena game for online play between players. It is a community created tech demo for the Leadwerks Engine 2.1 and showcase of Phoenix.Framework.
Networix is a Open Source Framework programmed in c# to allow users to script in lua, c# and GLSL in a OpenGL Environment using an object based interface.