For those interested here are the cheats:
# Cheat mode
While playing the game, press Up to display Niko's cellphone. Press Up again to access the keypad. Then, enter one of the following codes to activate the corresponding cheat function. Once a code has been entered correctly, a new "Cheats" menu option will be available on your phone, below "Options", where you can access the cheats without having to enter the phone number again. Note: Do not save the game after enabling a code to avoid unforeseen problems. Enabling some cheats may prevent achievements from being earned.
Full health
Dial "3625550100" into the cellphone. Note: This phone number translates to "DOC-555-0100". This code prevents the "Cleaned The Mean Streets", "Finish Him", "One Man Army", and "Walk Free" achievements from being earned.
Full health and ammunition
Dial "4825550100" into the cellphone. Note: This phone number translates to "GTA-555-0100". This code prevents the "Cleaned The Mean Streets" achievement from being earned.
Weapons tier 1
Dial "4865550100" into the cellphone. This will unlock the baseball bat, handgun, shotgun, MP5, M4, sniper rifle, RPG, and grenades. Note: This phone number translates to "GUN-555-0150". This code prevents the "Cleaned The Mean Streets" achievement from being earned.
Weapons tier 2
Dial "4865550150" into the cellphone. This will unlock the knife, Molotov cocktails, handgun, shotgun, Uzi, AK47, sniper rifle, and RPG. Note: This phone number translates to "GUN-555-0100". This code prevents the "Cleaned The Mean Streets" achievement from being earned.
Remove Niko's wanted level
Dial "2675550100" into the cellphone. Note: This phone number translates to "COP-555-0100". This code prevents the "One Man Army" and "Walk Free" achievements from being earned.
Add one star to Niko's wanted level
Dial "2675550150" into the cellphone. Note: This phone number translates to "COP-555-0150".
Spawn Annihilator police helicopter
Dial "3595550100" into the cellphone. Note: This phone number translates to "FLY-555-0100". This code prevents the "One Man Army" and "Walk Free" achievements from being earned.
Spawn Cognoscenti
Dial "2275550142" into the cellphone. Note: This phone number translates to "CAR-555-0142".
Spawn Comet
Dial "2275550175" into the cellphone. Note: This phone number translates to "CAR-555-0175".
Spawn FBI Buffalo
Dial "2275550100" into the cellphone. Note: This phone number translates to "CAR-555-0100".
Spawn Jetmax
Dial "9385550100" into the cellphone. Note: This phone number translates to "WET-555-0100".
Spawn NRG-900
Dial "6255550100" into the cellphone. Note: This phone number translates to "MBK-555-0100".
Spawn Sanchez
Dial "6255550150" into the cellphone. Note: This phone number translates to "MBK-555-0150".
Spawn SuperGT
Dial "2275550168" into the cellphone. Note: This phone number translates to "CAR-555-0168".
Spawn Turismo
Dial "2275550147" into the cellphone. Note: This phone number translates to "CAR-555-0147".
Change weather and brightness
Dial "4685550100" into the cellphone. Note: This phone number translates to "HOT-555-0100".
# Map locations
Enter "www.whattheydonotwantyoutoknow.com" into the in-game computers to view maps that reveal all weapon, health, armor, vehicle, pigeon, ramp/stunt, and entertainment locations.
# 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. -From: Khairol161
# Repairing engine
If the vehicle you are driving breaks down and the engine will not start, call 911, and your engine should start again.
# Fast travel
To avoid wasting time driving all the way across the city, call a taxi. They will take you to your destination for your mission, stores, safehouses, or even a waypoint marker. You can skip through the taxi ride, allowing you to travel across the entire city in about ten seconds. This can also be done during missions.
# Easy headshots
It is sometimes difficult to get headshots, which do count. With some practice, doing the following is an easy way to get headshots. Press [Auto-Aim], then use the Right Analog-stick to move the auto-aim target around your victim's body. Barely move the Right Analog-stick as you are shooting. This puts bullets in the chest and head, and results in an easy instant kill.
# Getting away from police
When running away from the cops, you will have a circular area in which they look for you. However, if you get out and another cop sees you, it changes. To use this to your advantage, barely get out of that circle, which you will see on your radar. Then, just sit there for about five seconds instead of flooring past it.
# Regaining health during missions
You can leave the mission area and go to a Cluckin' Bell, hotdog stand, etc. and eat food to replenish your health if you are low and cannot find a health pack. This is especially useful on missions where there are no health packs in sight. Note: You can also take a taxi to those locations during missions.
# Avoiding toll booths
Drive through any toll booth with any emergency vehicle with the sirens on. The booth attendant will open the gate, and you will save $5.
# $100 for all ringtones and themes
After getting the phone from Playboy X, go to the nearest Internet cafe. Buy all of the ringtones and themes from the ringtones site. Log out of the computer, and you will notice that you only paid $100 for all ringtones and themes.
