I'm surprised that no one has mentioned the level in cod 4 where you have to defend an area and wait for an evac chopper. It was really fun and easy on normal but on veteran it was just plain suicide. With the endless bots with their stupid infinite grenades blasting my hiding places and instakilling me over and over again. Not to mention the time limit that you have to get Macmillan (?) to the chopper when it finally arrives.