These codes can be entered via the keyboard while playing or while paused. A message will confirm correct code entry. 
Effect - Code 

Weapons (tier 1) - thugstools 
Weapons (tier 2) - professionaltools 
Weapons (tier 3) - nuttertools 
Armor - preciousprotection 
Health - aspirine 
Raise wanted level - youwonttakemealive 
Lower wanted level - leavemealone 
View media level when over two stars - chasestat 
Good weather - apleasantday 
Great weather - alovelyday 
Sunny weather - abitdrieg 
Stormy weather - catsanddogs 
Foggy weather - cantseeathing 
Rhino tank - panzer 
Faster game clock - lifeispassingmeby 
Faster game play - onspeed 
Slower game play - booooooring 
Destroy all cars - bigbang 
Pedestrians riot - fightfightfight 
Pedestrians attack you - nobodylikesme 
Pedestrians have weapons - ourgodgivenrighttobeararms 
Pedestrians enter your car - hopingirl 
Change wheel size - loadsoflittlethings 
Only wheels visible on cars - wheelsareallineed 
Dodo cars (flying) - comeflywithme 
Better driving skills - gripiseverything 
Bikini women with guns - chickswithguns 
Suicide - icanttakeitanymore 
Heavy traffic - miamitraffic 
Pink traffic - ahairdresserscar 
Black traffic - iwantitpaintedblack 
All traffic lights green - greenlight 
Romero's Hearse - thelastride 
Love Fist Limousine - rockandrollcar 
Trashmaster - rubbishcar 
Bloodring Banger (style 1) - travelinstyle 
Bloodring Banger (style 2) - gettherequickly 
Caddy - betterthanwalking 
Pedestrian costumes - stilllikedressingup 
Lance Vance costume - looklikelance 
Ken Rosenberg costume - mysonisalawyer 
Hilary King costume - ilooklikehilary 
Jezz Torent (Love Fist) costume - rockandrollman 
Dick (Love Fist) costume - weloveourdick 
Phil Cassaday costume - onearmedbandit 
Sonny Forelli costume - idonthavethemoneysonny 
Mercedes costume - foxylittlething 
Cars float on water - seaways 
Engines are faster - getthereveryfastindeed 
Engines very fast - getthereamazinglyfast 
All cars are faster - gettherefast 
Tommy groupies - fannymagnet 
Ricardo Diaz costume - cheatshavebeencracked 
Tommy smokes cigarette - certaindeath 
Tommy is fatter - deepfriedmarsbars 
Tommy has thin arms and legs - programmer 
Reguard target - airship