Enter the following during gameplay.

Tier 1 weapons :
Press R1, R2, L1, R2, Left, Down, Right, Up, Left, Down, Right, Up. This will unlock the weak weapons.

Tier 2 weapons:
Press R1, R2, L1, R2, Left, Down, Right, Up, Left, Down, Down, Left. This will unlock the medium weapons.

Tier 3 weapons:
Press R1, R2, L1, R2, Left, Down, Right, Up, Left, Down, Down, Down. This will unlock the powerful weapons.

Respect upgrade:
Press R1, R2, L1, X, Left, Down, Right, Up.

Bounty on your head:
Press Down, Up, Up, Up, X, R2, R1, L2, L2.

Armor, health, money, and street creds:
Press R1, R2, L1, X, Left, Down, Right, Up, Left, Down, Right, Up.

$250,000:
Press R1, R2, L1, X, Left, Down, Right, Up, Left, Down, Right, Up.

Raise wanted level:
Press R1, R1, Circle, R2, Left, Right, Left, Right, Left, Right.

Lower wanted level:
Press R1, R1, Circle, R2, Up, Down, Up, Down, Up, Down.

Perfect handling:
Press Triangle, R1, R1, Left, R1, L1, R2, L1. Press L3 to jump in a car.

Aggressive traffic:
Press R2, Circle, R1, L2, Left, R1, L1, R2, L2.

Faster cars:
Press Right, R1, Up, L2, L2, Left, R1, L1, R1, R1.

Drive on water:
Press Right, R2, Circle, R1, L2, Square, R1, R2.

Destroy cars:
Press R2, L2, R1, L1, L2, R2, Square, Triangle, Circle, Triangle, L2, L1.

Flying boats:
Press R2, Circle, Up, L1, Right, R1, Right, Up, Square, Triangle.

Spawn Rhino tank:
Press Circle, Circle, L1, Circle, Circle, Circle, L1, L2, R1, Triangle, Circle, Triangle.

Spawn Bloodring Banger:
Press Down, R1, Circle, L2, L2, X, R1, L1, Left, Left.

Spawn Ranger:
Press Up, Right, Right, L1, Right, Up, Square, L2.

Spawn Hotring Racer 1:
Press R1, Circle, R2, Right, L1, L2, X, X, Square, R1.

Spawn Hotring Racer 2:
Press R2, L1, Circle, Right, L1, R1, Right, Up, Circle, R2.

Spawn Romero:
Press Down, R2, Down, R1, L2, Left, R1, L1, Left, Right.

Spawn Stretch:
Press R2, Up, L2, Left, Left, R1, L1, Circle, Right.

Spawn Trashmaster:
Press Circle, R1, Circle, R1, Left, Left, R1, L1, Circle, Right.

Spawn Caddy:
Press Circle, L1, Up, R1, L2, X, R1, L1, Circle, X.

Spawn jetpack:
Press Left, Right, L1, L2, R1, R2, Up, Down, Left, Right.

Pedestrians riot:
Press Down, Left, Up, Left, X, R2, R1, L2, L1.

Pedestrians have weapons:
Press R2, R1, X, Triangle, X, Triangle, Up, Down.

Slow motion:
Press Triangle, Up, Right, Down, Square, R2, R1.

Fast motion:
Press Triangle, Up, Right, Down, L2, L1, Square.

Cloudy weather:
Press R2, X, L1, L1, L2, L2, L2, Triangle.

Very cloudy weather:
Press R2, X, L1, L1, L2, L2, L2, Square.

Foggy weather:
Press R2, X, L1, L1, L2, L2, L2, X.

Stormy weather:
Press R2, X, L1, L1, L2, L2, L2, Circle.

Sunny weather:
Press R2, X, L1, L1, L2, L2, L2, Triangle.

Very sunny weather:
Press R2, X, L1, L1, L2, L2, L2, Down.

Sunset Sky:
Press Left, Left, L2, R1, Right, Square, Square, L2, L1, X.

Twilight:
Press R2, X, L1, L1, L2, L2, L2, Square.

Day-time:
Press R2, X, L1, L1, L2, L2, L2, Down.

Night-time:
Press R2, X, L1, L1, L2, L2, L2, Triangle.

Commit suicide:
Press Right, L2, Down, R1, Left, Left, R1, L1, L2, L1.

Max Lung Capacity :
Press Down, Left, L1, Down, Down, R2, Down, L2, Down.

Affectionate women:
Press Circle, X, L1, L1, R2, X, X, Circle, Circle.

Four-star wanted level:
Press R1, R1, Circle, L1, Up, Down, Up, Down, Up, Down.

Invisible vehicles:
Press Triangle, L1, Triangle, R2, Square, L1, L1.

Huge BMX jumps:
Press Triangle, Square, Circle, Circle, Square, Circle, Circle, L1, L2, L2, R1, R2.

Maximum muscle:
Press Triangle, Up, Up, Left, Right, Square, Circle, Left.

Diesel Punches :
Press Up, Left, X, Triangle, R1, Circle, Circle, Circle, L2.

Beach Party:
Press Up, Up, Down, Down, Square, Circle, L1, R1, Triangle, Down.

Spawn parachute:
Press Left, Right, L1, L2, R1, R2, R2, Up, Down, Right, L1.

Spawn stunt plane:
Press Circle, Up, L1, L2, Down, R1, L1, L1, Left, Left, X, Triangle.

Vehicle of death:
Press L1, L2, L2, Up, Down, Down, Up, R1, R2, R2.

Sports Car Traffic:
Press Up, L1, R1, Up, Right, Up, X, L2, X, L1.

Spawn monster truck:
Press Right, Up, R1, R1, R1, Down, Triangle, Triangle, X, Circle, L1, L1.

Jump high:
Press Up, Up, Triangle, Triangle, Up, Up, Left, Right, Square, R2, R2.

Fatty:
Press Triangle, Up, Up, Left, Right, Square, Circle, Down.

Skinny:
Press Triangle, Up, Up, Left, Right, Square, Circle, Right.

Spawn an ATV:
Press Left, Left, Down, Down, Up, Up, Square, Circle, Triangle, R1, R2.

Spawn a Hydra:
Press Triangle, Triangle, Square, Circle, X, L1, L1, Down, Up.

Spawn a hovercraft:
Press Triangle, Triangle, Square, Circle, X, L1, L2, Down, Down.

Infinite cash:
Sit CJ down at the videogame machine in his hideout and then leave your PS2 for several hours. When you come back you'll have more money.

A million dollars:
Beat the four races that are marked as checkered flags on your map.

Double-headed dildo:
Go to the Los Santos police station (get busted if you can't find it), and look around in the showers.

Lemmings:
Go through the garage next to the gym in Las Venturas and out into the alleyway, then look to your right at the building across the street.

Headless:
Get a katana and enter a two-player mission. Cut Player One's head off with Player Two, then return to Single-Player mode.

Unlockable vehicles:

Bandito	Get 15 cars for the Import/Export dock
Bloodring Banger	Last a minute in the Bloodring
Bullet	Get all silver awards in driving school
Dune	Beat the score of 25 at the Dirt Ring
FCR-900	Get all silver awards in bike school
Freeway	Get all bronze awards in bike school
HotKnife	Get all gold awards in driving school
Hotring Racer	Get first place in the 8-track
Hydra	Beat the "Vertical Bird" mission
JetMax	Get all gold awards in boat school
Marquis	Get all bronze awards in boat school
Monster Car	Win it by beating 8-track
NRG-500	Get all gold awards at Bike School
Rustler	Get all bronze awards in pilot school
Squallo	Get all silver awards in boat school
Stunt Plane	Get all silver awards in pilot school
Super GT	Get all bronze awards in driving school
Turismo	Get 20 vehicles for the Import/Export dock
Vortex	Get 25 vehicles for the Import/Export dock
Windsor	Get 10 vehicles for the Import/Export dock

Taxi Nitro boosts:
Get 50 fares in a taxi.

150 max armor:
Beat 12 vigilante missions.

150 max health:
Beat 12 ambulance missions.

Get laid and get paid:
Become a level 10 pimp.

Fireproof CJ:
Become a level 12 firefighter.

Own RS Haul:
Become a level 8 trucker.

Free ammo:
If you're low on ammo with a particular weapon, enter an Ammu-nation shooting range with it equipped, and then walk out again.

Foil attacks on your neighborhood:
If you hear that one of your territories is under attack, just go to a safe-house and save the game.

Keep weapons if busted:
Date Barbara.

Keep weapons if wasted:
Date Katie.

Unlockable suits:
Get your relationship to 100% with the indicated woman.

Super bike jump:
Get on a bicycle with a handgun, mini-SMG, or SMG equipped. Then, do a bunny-hop and tap the circle button once, very quickly.

Infinite nitro:
Equip a car with nitrous, and save it in your garage. Then, while the car is in the garage, activate the nitrous, and blow it up; it will respawn with infinite nitrous.

Skip Pilot School and Get Your License:
In the first city, hop the fence and get into SHAMAL. Keep flying South until you get your license and gain access to every airport.