Call of Duty 4: Modern Warfare

During the "All Ghillied Up" mission, you will come across a wild dog eating a dead soldier's remains. You will be told to leave it alone, but if you want probably the most difficult challenge in the game, shoot it. You will be attacked by a large pack of angry dogs.

In the mission when you play Cpt. Price, you will encounter a wild dog eating a man. You are told to leave it alone, but if you kill it you will hear dogs growling. You are then attacked by a large pack of them. This is the best way to practice your dog killing skills, but be warned. You must save your comrade, because if he dies you must start over again.

When playing the Marine's side (wooden shacks and the field), in the back building with the turret there is a dumpster besides it, against a ground window. Crouch and sit inside the building behind the dumpster. You can snipe out of the window down the side alley. Also in the back building, go up the stairs and turn left. There is a table beside the stairs. Climb onto the table then onto the railing (banister). This may take a few attempts. Jump across the stairs onto the gray ledge with the fencing. From here you can snipe the entrance to the field and the big concrete building on your side.

When playing on the OpFor/Spetznas side (the destroyed concrete buildings), as soon as you start go straight to the hole in the ground. Directly in front of it should be two roadblocks. Go prone (lie down) and look between them. From here you can snipe across the street to the opposite concrete building (helicopters can see you).

When playing on the OpFor/Spetznas side, go down the street and up the stairs on the left. There is a sheet metal ledge that you can stand on. Stand on the edge of the sheet metal and look to the left (back to your spawn point). You can see an opening in the side of the building. Sprint jump off the end into the side of the building. This may require a few attempts.

To unlock Arcade Mode, beat the game once through on any difficulty level. Arcade Mode itself is split into two options - Full Challenge or Level Challenge - that add extra replayability to the game.

On the Marines side of "Flag B" is sheet metal guarding the top of a building. Climb the ladder to get to the top. To stand on the sheet metal itself, climb onto a ledge and slowly go back and forth until you see the "Climb" option. Make your way to the ledge besides the building overlooking the tiny enclosure. You will see a white radiator. Jump into it. There are little knobs sticking out of the buildings that look like this.
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Radiator>[l] l l l l

Once you get the Red Dot Scope addon to your weapons, use it over the ACOG scope. The red dot will not enhance or take away anything and provides a better aimpoint on most weapons. The ACOG scope will actually add more range to your weapon, but take away accuracy which accomplishes almost nothing; especially so for snipers because it takes away range and adds nothing.