Gears of War Judgment Mods (Noclip, Godmode unlimited Ammo) http://www.youtube.com/watch?v=CjSIOpFTSG4
No, there haven't been any public gpd mods for GOW3 so you can assume there won't be any for this game since it almost has the same game code. Look and see if there are any gpd mods for an unreal engine based game, there aren't any if i recall.
I'm one mission away of getting 3 stars in all missions so I guess I won't be needing it that much anymore haha