The Zombie engine is an open source game engine and framework based in The Nebula Device 2, the open source engine from Radon Labs. Developed by Tragnarion Studios, it is mainly oriented towards the creation of multiplayer PC action games.
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.