Grand Theft Auto IV Cheats

Easy money
Go to an ATM, then cause a traffic jam to the area. Wait for someone to take money from the ATM, then kill him or her. Make sure to block any nearby roads so the ambulance cannot get to the murdered victim. Take the money they dropped on the ground. Then, run a short distance away, and go back. The money should have respawned on the ground. You can repeat this as many times as desired. You can also kill more people taking their money from the ATM to increase the amount of money that respawns.

Repairing the engine
If the vehicle you are driving breaks down and the engine will not start, call 911, and your engine should start again.

Unlockables
Annihilator Helicopter: Kill all 200 Flying Rats
Rastah Color Huntley SUV: Complete 10 Package Delivery missions
Remove Ammo Limit: Get 100% completion

Friendship Bonuses
By gaining friendship with the following people can benefit you in many ways.

Boom? (Call Packie for him to make you a car bomb): Gain 75% friendship with Packie
Chopper Ride (He will pick you up in his helicopter): Gain 70% Friendship with Brucie
Discount Guns (Buy weapons at a cheaper price from Lil Jacob): Gain 60% friendship with Little Jacob
Extra Help (A car of gang members will be sent to help you out): Gain 60% friendship with Dwayne
Free Ride (Call for a taxi): Gain 60% friendship with Roman

Get a Statue of Liberty T-shirt
Go to the statue of liberty and walk up to the second level. Walk through the door (it doesn't swing open, just go through it) and the game will load for a second and you will walk out with a new t-shit with the statue of liberty on it.

Rastah Color Huntley SUV
To Unlock Rastah Color Huntley SUV you have to successfully complete 10 package delivery mission.

Wheelie Rider Achievement
Grab a motor bike and approach Francis International airport then go to the one end of runway, now accelerate your bike and do a wheelie, to do this you have to press left analog stick down for 500 feet to get this achievement. Runway is ideal here because here you have a very long and clean path where you can drive without any trouble.

Rolled Over Achievement
Get a fast car and go to the runway e.g Super GT, Infernus etc. Find a yellow ramp scattered along the runway grass then hit one of the ramp with high speed in a way that only half of your car hits the ramp, this will give you enough spins to get the achievement.

At Algonquin Bridge which connects Dukes to Algonquin locate the part where the lanes split at the bridhge when going towards westbound. There is a small ramp at the split, hit that ramp at very high speed and it shall roll over your car several times and if you land in the lower area you will get more spins.

Walk Free Achievement
Go to the airport runway in a car, get out of car and you will instantly score a four star wanted level which you require to get the achievement. Now drive or run to the end of runway and you will get the achievement.

Find cops and if you kill them your wanted level will rise. When you have scored 4 star wanted level get into the vehicle and drive into subway tunnel. As soon as you leave the flashing wanted circle and your wanted level disappears you will score the achievement.

Join The Midnight Club Achievement
To get the achievement keep joining and quitting games/matches until you become the host. Then setup the lap no to 1 and start a new helicopter race with few opponents.

Jizz Reference
There is a detergent inside the laundromat which is being used and displayed above the back washing machine is Jizz! Big Washing Power, its an obvious attempt at cruel humor.

Chain Reaction Achievement
To get this achievement, make a traffic jam in the enclosed area e.g booth tunnel, you can do this by blocking off both lanes with two automobiles. When cars back up, steal some of them and squeeze them in between others so that there are 3 or 4 next to each other then throw a grenade at automobiles in front and use the RPG to destroy the others.

Spider Man Reference
Occasionally pedestrians passing by you will say "Look it's your friendly neighbour.. oh, no never mind"

Brown Note Reference
Around Faustin's house there is a reference to a great legendary musical note. When you are in that area go to dead end about a block away towards the water. Now hop over the fence which is on your left while you are facing the water, there should be a man sitting on a beach reading a book with title "The Brown Note". Musician's joke that this is a note that when played causes bowel movements by the person playing it.

Completion
All of the following tasks must be completed to achieve a 100% completion rating.

Activities - Defeat the CPU or an in-game friend at all activities at least once.
Car Thefts - Deliver all 30 vehicles to the garage.
Flying Rats - Find and kill all 200 pigeons.
Missions - Complete all 90 main story and procedural missions.
Most Wanted - Kill all 30 pedestrians on the list.
Random Characters - Find all 14 random characters and complete their encounter missions (except Jeff, Cherise, Clarence, and Ivan).
Unique Stunt Jumps - Complete all 50 jumps.
Vigilante - Complete 20 crimes.

Two bits!
Get any type of car and go to a large traffic jam. Use the horn to do the "Shave and a haircut" and stop, one of the many other cars should do the "two bits". You must listen carefully because it might be done by a pedestrian instead!

Easter Egg: Fire Truck Madness
If you boost a fire truck, press the fire button while driving around. This will allow you to shoot the super-powerful water cannon at anyone around you. Watching people react to getting shot with high-speed water is hilarious.

Easter Egg: Prank Calls
Here's something funny to try. During your adventure through Liberty City, you may find phone numbers written in inconspicuous places, such as on the side of a building or in the subway. If you dial these numbers, you'll usually get someone on the other end who you can subsequently prank.

Mr. tasty + GTA Theme Cheat
When inside a Mr. Tasty Ice Cream truck, one of the the songs the truck plays is called the GTA Theme, in a cycle order it is usually played after Flight of the Bumblebee. While playing the song, call ZiT, and a text message will confirm telling you the name of the song. As soon as the message is answered, a Cheat Activated confirmation will appear, and the cheat will appear in the Cheat section in your phone. Cheat gives you full healith and Body Armor.