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Adds a set of weapons and ammunition.
It changes nothing beyond the player, so normal play can continue after the mission.

Codes are typed directly during play, with no console or menu. They can therefore trigger accidentally, and some effects require a restart to remove.
GTA III has no cheat interface. Codes are typed as ordinary text during play and accepted with a short message. There is no list of active effects from which unwanted changes can be disabled.
Most codes are harmless, such as health, ammunition and money. The dangerous group changes the surrounding world: pedestrian behaviour, vehicle physics or civilian weapons. Some of these effects are one-way and repeating the code does not remove them.
The codes are ordered by their effect on a run rather than alphabetically. The list is deliberately not exhaustive because spelling and effects differ between editions; it covers codes that work consistently in the original PC version.
Adds a set of weapons and ammunition.
It changes nothing beyond the player, so normal play can continue after the mission.
Restores health to full.
The most commonly used and least intrusive code.
Restores armour.
Some editions list the spelling TORTOISE. Try the other if one does not work.
Adds a quarter of a million to the wallet.
Money alone does not break a run, but removes the purpose of many side activities.
Changes the player's appearance.
A visual effect with no gameplay impact. Using it again replaces the change.
Lowers the wanted level.
During a pursuit-based mission, it can disrupt the script and prevent completion.
Raises the wanted level.
Useful for testing higher levels, but unhelpful during a delivery.
Spawns a Rhino tank near the player.
It needs open space. On a narrow street it may become stuck and damage nearby cars.
Destroys nearby vehicles.
It also destroys mission vehicles, the most common way to ruin the current task with a cheat.
Makes cars fly.
It changes the physics of all vehicles, including AI traffic. Timed missions and escorts do not cope well.
Improves vehicle cornering.
The least disruptive code in the group that changes physics.
Hides vehicle bodies, leaving the wheels visible.
A visual effect that makes judging distances in traffic harder.
Starts a riot in which pedestrians attack one another.
The same code usually cannot disable it. Quit and load a save for a reliable return to normal.
Arms pedestrians in the street.
It fundamentally changes travel difficulty and, combined with riots, turns normal driving into a firefight.
Makes pedestrians attack the player.
Collecting and service missions become nearly impossible with this effect.
Enables dismemberment.
A purely visual change to hits that does not alter scripts.
Sets sunny weather.
The best option for taking pictures and navigating terrain.
Sets cloudy weather.
Starts rain.
Rain noticeably changes vehicle behaviour on the road, so it is not merely cosmetic.
Enables dense fog.
It sharply reduces visibility and is a poor choice for timed drives.
Speeds up the passage of game time.
Enables slow motion.
Used for precise jumps and viewing details that pass too quickly at normal speed.
Before entering the first code, create a separate save and do not overwrite the clean one.
GTA III has enough slots. Sacrificing one is cheaper than losing twenty hours.
Effects that alter pedestrians and physics can be written into the save and survive loading.
If that happens, only an older save restores the clean state, hence the separate slot.
Triggering a cheat during a task is the most common cause of a mission that cannot be completed.
The script expects a particular vehicle, enemy count or wanted level. A code can remove that requirement.
These text codes are for PC. Console versions use button combinations and are not interchangeable with this list.
Definitive Edition has its own set and on some platforms temporarily disables achievement unlocks after cheats are used.
Answers to the main questions about this topic
Entering a code alone does not block completion in the classic PC version. It can still break a run indirectly: a code used during a mission may prevent completion, and some GTA III missions are permanently missable.
For most codes, enter the same code again. Effects that change pedestrian behaviour are an exception; repeating them often fails, so loading a save from before activation is the only reliable solution.
Some are. Changes to the world and pedestrians can survive saving and loading, while restored health or ammunition is a one-off effect. Use a separate save slot for cheats.
Not reliably. Definitive Edition uses a different technical base, has its own code set and may temporarily disable achievement unlocks after a cheat. This list covers the original PC version.
No. GTA III has no code that unlocks the story ending or fills the completion percentage. Claims otherwise come from unverified copied lists.