On some versions a sound will confirm correct code entry... And all codes should be entered DURING GAMEPLAY!!! All Weapons:
During gameplay press R2, R2, L1, R2, Left, Down, Right, Up, Left, Down, Right, Up. Blow Up All Cars:
During gameplay press L2, R2, L1, R1, L2, R2, Triangle, Square, Circle, Triangle, L2, L1. Clear Wanted Meter:
During gameplay press R2, R2, L1, R2, Up, Down, Up, Down, Up, Down. Control Time:
During gameplay press Circle, Circle, Circle, Square, Square, Square, Square, Square, L1, Triangle, Circle, Triangle. Dodo Car Mode:
During gameplay press R1, L1, R2, L1, Left, R1, R1, Triangle. Free Tank:
Put all weapons away and press Circle(6), R1, L2, L1, Triangle, Circle, Triangle. Full Armor:
During gameplay press R2, R2, L1, L2, Left, Down, Right, Up, Left, Down, Right, Up. Full Health:
During gameplay press R2, R2, L1, R1, Left, Down, Right, Up, Left, Down, Right, Up. Increase Wanted Meter:
R2, R2, L1, R2, Left, Right, Left, Right, Left, Right. Lots of Money:
R2, R2, L1, L1 Left, Down, Right, Up, Left, Down, Right, Up. Nasty Limbs:
Square, L1, Circle, Down, L1, R1, Triangle, Right, L1, X. Not so wanted:
R2, R2, L1, R2, Up, Down, Up, Down, Up, Down. People Have Weapons:
During gameplay press R2, R1, Triangle, X, L2, L1, Up, Down. Sluggish Turning:
During gameplay press Right, R2, Circle, R1, L2, Down, L1, R1. Violent People:
During gameplay press Down, Up, Left, Up, X, R1, R2, L2, L1. Wear Any Outfit:
During gameplay press Right, Down, Left, Up, L1, L2, Up, Left, Down, Right. Weather - Clear:
During gameplay press L1, L2, R1, R2, R2, R1, L2, Triangle. Weather - Foggy:
During gameplay press L1, L2, R1, R2, R2, R1, L2, X. Weather - Rainy:
During gameplay press L1, L2, R1, R2, R2, R1, L2, Circle. Weather - Stormy:
During gameplay press L1, L2, R1, R2, R2, R1, L2, Square. Who Are You?:
During gameplay press Right, Down, Left, Up, L1, L2, Up, Left, Down, Right.

Here is our ultimate cheat collection for Grand Theft Auto 3...

Enter any of the following during gameplay, for most of these you will get a message confirming correct code entry.

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Weapons, health and armour Cheats
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Weapons tier(1):
r1, r2, l1, r2, left, down, right, up, left, down, right, up.

Weapons tier(2):
r1, r2, l1, r2, left, down, right, up, left, down, down, down.

Weapons tier(3):
r1, r2, l1, r2, left, down, right, up, left, down, down, left.

Health cheat:
r1, r2, l1, o, left, down, right, up, left, down, right, up.

Armour cheat:
r1, r2, l1, x, left, down, right, up, left, down, right, up.

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Pedestrian Cheats
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Pedestrians Riot:
R1, L1, R2, L1, Left, R1, R1, Triangle

Pedestrians Hate You:
Down, Up, Left, up, X, R1, R2, L1, L2

Pedestrians Have Guns:
R2, R1, Triangle, X, L2, L1, Up, Down

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Wanted Level Cheats
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Lose Wanted Level:
R2, R2, L1, R2, Up, Down, Up, Down, Up, Down

2 Star Wanted Level:
R2, R2, L1, R2, Left, Right, Left, Right, Left, Right

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Vehicle Cheats
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Better Handling:
R1, L1, R2, L1, Left, R1, R1, Triangle

Vehicle Health:
R2, R2, L1, R1, Left, Down, Right, Up, Left, Down, Right, Up

Flying Vehicles:
Right, R2, Circle, R1, L2, Down, L1, R1

Invisible Vehicles:
L1, L1, Square, R2, Triangle, L1, Triangle

Blow Up Car:
L2, R2, L1, R1, L2, R2, Triangle, Square, Circle, Triangle, L2, L1

Tank:
Circle x6, R1, L2, L1, Triangle, Circle, Triangle

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Weather Cheats
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Weather Cheats
Foggy:
L1, L2, R1, R2, R2, R1, L2, X

Cloudy:
L1, L2, R1, R2, R2, R1, L2, Square

Rain:
L1, L2, R1, R2, R2, R1, L2, Circle

Normal:
L1, L2, R1, R2, R2, R1, L2, Triangle

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Time Cheats
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Speed Up Time:
Circle x3, Square x5, L1, Triangle, Circle, Triangle

Slower Game Play:
Triangle, Up, Right, Down, Square, R1, and R2

Speed Up Everything:
Triangle, Up, Right, Down, Square, L1, and L2

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Other Cheats
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Gore: Square, L1, Circle, Down, L1, R1, Triangle, Right, L1, X
(You’ll know it worked when you aim at some ones leg and it falls off when you shoot it.)