Burgundy, France: Invisible Turret:

This trick requires two players. Go to the building with the MG 42. This is the building that is not destroyed. Have one player jump on top of the MG 42. Have the other player start jumping behind him. The player on the MG 42 must face out the window. When the jumping player is in mid-air, have the other player get on the MG 42. He should be invisible but still able to shoot the turret. He will be almost invincible, requiring two or three grenades directly on him to kill him. Remember that it only works if the player is directly on top of the MG 42.