Some toys for modelers and level designers here
Sorry for this theme but I am always looking for new easy nice and high qualitty engines - trying modeling, mapping and creating games .
Here are interesting free one , for enthusiastics
Platinum Arts Sandbox free 3d gamemaker - powerfull , based on cube 2 engine - http://sandboxgamemaker.com/
Unity 3D - powerfull engine, game editor http://unity3d.com
Unreal Developement Kit - Unreal engine 3 now free! http://www.udk.com/
Spring engine - http://springrts.com/
Ngene Tech engine - http://ngene.wikidot.com/
GSP engine - nice http://www.melog.ch/dropper/
G3D innovation - http://g3d.sourceforge.net/index.html
Atmosphir - easy http://atmosphir.com/
Esenthel game engine - nice www.esenthel.com
Delta 3D - can import 3ds, obj and more http://www.delta3d.org/
AntiryadGX http://www.arkham-development.com/
CA 3D engine - very easy and nice, powerfull , is possible use gmax - md2, md5, obj, 3ds import and more http://www.ca3d-engine.de
Cast II engine www.casteng.com
Reality Factory - is based on Genesis 3D engine, is possible use gmax http://www.realityfactory.info/cms/
Just for fun
Sorry for so many links