Blender
From Game Making Tools Wiki
Blender is mostly recognised as a free 3-D modeller (with an idiosyncratic interface), but it also functions as a game maker and video editor.
Bforartists
Bforartists is a fork of Blender aimed at remedying Blender's often complained about interface, making it more intuitive. It's probably not quite ready to use at, but worth keeping an eye on!