Call of Duty 4: Modern Warfare

Beat the game on any difficulty and let the credits run all the way through. When they finish, you'll start another mission. This mission takes place on a plane the resembles Air Force One, wherein you must fight your way through a hoard of baddies, save the V.I.P. and escape the plane in less than 2 minutes.

Also, when you finish the game, you unlock the Arcade Mode.

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.

Go to the location of the first Intel Piece, located at the top of the ladder in the first church. Get the Intel Piece and fall back down. You will die and start out getting the Intel Piece again. The Intel Piece keeps adding to the total number that you have. Repeat this process until you have 30 Intel Pieces.

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.

Successfully complete the game.