Remember to never save game after enabling cheat mode!
Weapons Package #1
PC: 
Xbox: 
PS2:
Brass Knuckles, Bat, 9mm, Shotgun, Micro MP5, AK-47, Rifle, Rocket Launcher, Molotovs, Spray Can.
Weapons Package #2
Xbox:
PS2:
Knife, Desert Eagle, Sawed-Off, Tec-9, M4, Sniper Rifle, Flame Thrower, Grenades, Fire Estinguisher.
Weapons Package #3
Xbox:
PS2:
Chainsaw, Silenced 9mm, Spaz, MP5, M4, Sniper Rifle, Heat Seaking Rocket Laucher, Remote Explosives.
$250,000 & Full Health & Armor
Xbox: 
PS2: 
Infinite Health
Xbox:
PS2:
Makes you mostly bulletproof, and fire, punches and melee attacks don't hurt you anymore. You can still be hurt by explosions, falling, getting run over, and drowning.
Infinite Ammo
Xbox: 
PS2: 
Infinite Oxygen (Lung Capacity)
Xbox:
PS2:
Swim underwater and never have to worry about drowning!
Commit Suicide
Xbox:
PS2:
Adrenaline Mode
Xbox:
PS2:
Never Get Hungry
Xbox: 
PS2:
Hitman level in all weapons
Xbox:
PS2:
Automatically gives you the hitman level for all weapons.
Never Wanted
Xbox: 
PS2: 
Wanted level never increases. Doesn't erase stars you already have.
6 Star Wanted Level
Xbox:
PS2:
Lower Wanted Level
Xbox:
PS2:
Decreases the wanted level by decrements of 2 each time the the code is used.
Recruit Anyone (9MM)
Xbox:
PS2:
Recruit normal pedestrians into your gang. If they don't normally have a weapon, they'll carry a 9mm.
Recruit Anyone (Rocket Launcher)
Xbox:
PS2:
Recruits get rocket launchers if they don't already have weapons.
Increase Wanted Level
Xbox:
PS2:
Increases the wanted level by increments of 2 each time the the code is used.
Maximum Vehicle Stats
Xbox:
PS2:
Maximum Respect
Xbox:
PS2:
Maximum Sex Appeal
Xbox:
PS2:
Really Fat CJ
Xbox:
PS2:
Fat level for CJ goes to maximum.
Really Skinny CJ
Xbox:
PS2:
Muscle and fat levels are dropped to zero.
Really Muscled CJ
Xbox:
PS2:
Muscle level for CJ goes to maximum.
Gangs Control the Streets
Xbox:
PS2:
Streets deserted except for gunmen fighting in the streets. No cops or regular citizens. No traffic except in gang territories.
Gang Members Everywhere
Xbox:
PS2:
Gangs will appear all over the state, even in areas where you wouldn't normally expect to find them (Ballas in Las Venturas, for example). Similar to the 'Gangs Rule the Streets' cheat, except pedestrians are basically "replaced" by gangsters, so they drive around etc aswell.
Hunter
Xbox:
PS2:
Tanker
Xbox:
PS2:
Dozer
Xbox:
PS2:
Jetpack
Xbox:
PS2:
Parachute
Xbox:
PS2:
Katana
Xbox:
PS2:
Rhino/Tank
Xbox:
PS2:
Ranger
Xbox:
PS2:
Caddy
Xbox:
PS2:
Hotring Racer 1
Xbox:
PS2:
Hotring Racer 2
Xbox:
PS2:
Bloodring Banger
Xbox:
PS2:
Stretch Limo
Xbox:
PS2:
Romero's Hearse
Xbox:
PS2:
Trashmaster
Xbox:
PS2:
Quad
Xbox:
PS2:
Hydra
Xbox:
PS2:
Vortex
Xbox:
PS2:
Monster Truck
Xbox:
PS2:
Stunt Plane
Xbox:
PS2:
All Cars Have Nitrous
Xbox:
PS2:
Cars Float Away
Xbox:
PS2:
Bump into another vehicle and it will rise into the air and float away. It will float in whichever direction you hit it from, and the angle at which it floats depends on the force you hit it at.
Traffic is Country Vehicles
Xbox:
PS2:
All traffic is replaced with vehicles normally found in the countryside.
Traffic is Country Vehicles (minus hillbilly gear)
Xbox:
PS2:
This is the same as the other 'traffic is country vehicles' cheat, although you don't recieve the hillbilly gear.
Traffic is Crap Cars
Xbox:
PS2:
Invisible Cars
Xbox:
PS2:
All vehicles invisible except motorbikes (only the wheels are invisible).
Improved Handling (Hit R3 to jump)
Xbox:
PS2:
Faster Cars
Xbox:
PS2:
Aggressive Traffic
Xbox:
PS2:
Reduced Traffic
Xbox:
PS2:
No peds and only an occasional car on the street. Parked cars still spawn. Great for cruising. Still enough cars that you're not totally stranded if you wreck your ride.
Drive on Water
Xbox:
PS2:
Destroy all vehicles
Xbox:
PS2:
Taxis have nitrous
Xbox:
PS2:
Cannot be turned off. When code is typed in a second time, the "cheat activated" text is again displayed.
Fast/Rare cars appear regularly
Xbox:
PS2:
Black Traffic
Xbox:
PS2:
Pink Traffic
Xbox:
PS2:
Traffic Lights Green
Xbox:
PS2:
Cars Fly
Xbox:
PS2:
But not like they did in Vice City. The controls are more accurate, and the whole process is just like flying a normal plane.
Boats Fly
Xbox:
PS2:
Vehicle of Death
Xbox:
PS2:
Any vehicle the player is using becomes invincible and gains the ability to instantly destroy anything it touches.
Massive Bunny Hops
Xbox:
PS2:
CJ has the ability to bunny hop on the BMX over massive distances.
Chaos Mode
Xbox:
PS2:
Pedestrians riot, just like they do in the final mission strand. Houses are on fire, people run down the streets carrying TV's and so on..
Elvis is Alive
Xbox:
PS2:
All pedestrians look like Elvis Presley,
Peds Attack (Guns)
Xbox:
PS2:
Ninja Theme
Xbox:
PS2:
Peds are all Asian dudes with katanas. Traffic is black PCJ-600's, and BF-400's, and FCR-900's. Even cop cars are all black. Get katana.
Funhouse Theme
Xbox:
PS2:
CJ's appearance changes - a clown nose appears, red hair etc. Pedestrians are replaced with cluckin' bell/well stacked pizza/burger shot workers, and so on. Ice cream vans are seen regularly, and more..
Slut Magnet
Xbox:
PS2:
Attract sluts with sex toys & get gimp suit.
Full Weapon Aiming Whilst Driving
Xbox:
PS2:
Aim and shoot at passing pedestrians/vehicles, just like your homies would during drive-by shootings.
Peds Come After You
Xbox:
PS2:
Pedestrians Riot
Xbox:
PS2:
Pedestrians Carry Weapons
Xbox:
PS2:
Move Fast
Xbox:
PS2:
Jump High
Xbox:
PS2:
CJ can now jump 10 times as high as before. Falling down will deduct from health.
Mega Punch
Xbox:
PS2:
Punches send people flying into the next block. One hit kills. Watch out, peds have it too!
Beach Party
Xbox:
PS2:
Pedestrians turn into girls wearing swimsuits. Vehicles are also beach style and CJ will be dressed in shorts and sandals.
Orange Sky
Xbox:
PS2:
This cheat makes the sky look just like in the early preview screenshots. Just like those early preview screens they released, like the one where Carl has a giant hand. This cheat locks the clock at 21:00.
Speed Up Clock
Xbox:
PS2:
Slow Down Clock
Xbox:
PS2:
Sunny
Xbox:
PS2:
Really Sunny
Xbox:
PS2:
Cloudy
Xbox:
PS2:
Foggy
Xbox:
PS2:
Stormy
Xbox:
PS2:
Sandstorm
Xbox:
PS2:
Always Midnight
Xbox:
PS2:
Clock stopped at 00:00. Weird sudden weather changes. If you kill yourself, the time stays at 12:00.