Okay, i`ve found A LOT of free game engines, some of them which are more proffesional than others here are they:
Unreal development Kit - The game engien used to develop GoW the most selling XboX 360 game ever
Blender Game Engine - well, yall know bout this one...
Untiy3D - cross platform GE FTW!
Glest/GAE/MG [of course, who would forget here?] - best game engine ever!
any else you guys got?