I spent a lot of time yesterday finishing up all the achievements for Call of Duty 4 (Mile High Club is insanely difficult, but doable.) I got all 30 of the "enemy intel" items, which are laptops scattered around the levels in out-of-the-way places. I used a YouTube video to locate them.
After you get a certain amount of them, you will unlock a new cheat that you can activate at any time during a mission. There are 8 cheats, with a range of different changes. If you do enter cheat mode, finishing that mission does not count and you cannot earn achievements.
CoD Noir
Basically just turns the game into black and white.
Photo-Negative
Inverts the game's colors.
Super Contrast
The contrast between colors in the game increases.
You can combine the above three and turn them all on at once.
Ragtime Warfare
One of the best ones, it takes out all the sounds, increases the game's speed, gives it a early 20th century film feel (sepia, scratches on the screen,) and plays piano music in the background. It's very funny to watch. Cannot be combined with the above three color-changing cheats.
Cluster Bombs
All grenades explode into about 5 more grenades, which then explode.
A Bad Year
Enemies explode into several tires when shot. Very weird.
Slow-Mo Ability
Clicking the right thumbstick will put the game into slow-motion. This is easily my favorite perk. I love running into a room in slow motion and getting headshots with a pistol (there's a Desert Eagle you can get on Crew Expendable.) Can't be combined with Ragtime Warrior.
Infinite Ammo
Figure it out for yourself.
There may be a YouTube video for these cheats, but I'm not your search function.
After you get a certain amount of them, you will unlock a new cheat that you can activate at any time during a mission. There are 8 cheats, with a range of different changes. If you do enter cheat mode, finishing that mission does not count and you cannot earn achievements.
CoD Noir
Basically just turns the game into black and white.
Photo-Negative
Inverts the game's colors.
Super Contrast
The contrast between colors in the game increases.
You can combine the above three and turn them all on at once.
Ragtime Warfare
One of the best ones, it takes out all the sounds, increases the game's speed, gives it a early 20th century film feel (sepia, scratches on the screen,) and plays piano music in the background. It's very funny to watch. Cannot be combined with the above three color-changing cheats.
Cluster Bombs
All grenades explode into about 5 more grenades, which then explode.
A Bad Year
Enemies explode into several tires when shot. Very weird.
Slow-Mo Ability
Clicking the right thumbstick will put the game into slow-motion. This is easily my favorite perk. I love running into a room in slow motion and getting headshots with a pistol (there's a Desert Eagle you can get on Crew Expendable.) Can't be combined with Ragtime Warrior.
Infinite Ammo
Figure it out for yourself.
There may be a YouTube video for these cheats, but I'm not your search function.
