All Cars and Levels
Type KEVWOZEAR at the screen where you pick you can change your car or the
race. You should here a clanking sound. You now have access to all vehicles,
stages and you can upgrade your car's stats to CHEAT.

All Cars in Network Mode
At the screen where you can pick what type of network game you wanna play,
type in JOYRIDER. The host will have access to all of the cars (including
cheat cars), and the client will only have access to the non-cheat cars.

Type In Cheats
(Type these cheats while your are racing around like a maniac...)

5 Recovery Vouchers - ICECREAMHOLE
Acme Damage Magnifier - WEHATEMARIO
Blind Pedestrians - HAMSTERSEX
Bouncey Bouncey - CHICKENFODDER
Disable Timer - SEXWITHFISH
Drugs - INTHELOFT
Electro Bastard Ray - RUSSFORMARIO
Explosive Pedestrians - SUPERHOOPS
Fast Opponents - YUMMYLARD
Fast Police - YAKATTACK
Final Lap - MRCURSORSCOOL
Free Repairs - SPAMFRITTERS
Frozen Opponents - SPAMACCIDENTS
Frozen Police - NASALSMEAR
Giant Pedestrians - SMALLUDDERS
Greased Tires - BENFORMARIO
Grip-O-Matic Tires - BOYSFROMTHEBUSH
Hot Rod - IGLOOFUN
Instant Handbrake - SPAMFORREST
Instant Repair - INTHEWAR
Invunerablity - SPOONREASON
Loose Springs - BUYOURNEXTGAME
Lunar Gravity - RABBITDREAMER
Mega Turbo - SOAPYTITWANKS
Mine - BILLANDBEN
Money Bonus - GIVEMELARD
Oh Dear, Bodywork Trashed! - BIGBOTTOM
Pedestrian Harvest - TRAMSARESUPER
Pedestrians On Map - ILOVENOBBY
Pedestrians Glued To Ground - SPAMSPAMSPAMSPAM
Pedestrian Respawn - NAUGHTYTORTY
Solid Granite Car - KEEPITHAPPINESS
Strange Gravity - IHAVESOMESPAM
Time Bonus - MILKYSMILES
Turbo Pedestrians - FUNNYJAM
Underwater Ability - GOOGLEPLEX
Vesuvian Corpses - ISLANDRULES
Wall Climber - SECRETCOWS

pds41 says: "I understand that typing in IBETYOUCANTPRINTCUNT enters developer mode (then F4 or Shift-F4 to switch between modes) - source: Carmageddon Wiki".

A Weird Cheat
Type IWANTTOFIDDLE at the screen where you pick your car etc... It makes a
sound, but I have no idea what it does. Addendum: JMICH says : "As I recall, this one decrypts the car data so you are free to modify their stats easier. Not sure if you need to encrypt them again before using them or not."

I got these cheats from a guide on Gamefaqs.com by 007 , and he got most of them from www.gamesages.com
and the the 2nd PC PowerPlay GAME GUIDE.

I understand that typing in IBETYOUCANTPRINTCUNT enters developer mode (then F4 or Shift-F4 to switch between modes) - source: carmageddon wiki, but I'm sure I've heard this before somewhere.

There's probably a reason why it's not usually a printed out cheat code though...

If there are any cheats that are not in this list, and you notify me of their existence, i will put them here, crediting you.

JMICH, I've heard that it makes it so that every car can be stolen and used.

No, it's not required to encrypt them again. Everything will work fine. I did few modification myself - fixing broken cars (Lady Bug's Bugutti, Sinthea's Sled) and making Vlad's Annihilator II stealworthy (it's not by default, but unlike other non-stealworthy cars, it lacks a CHEAT banner).

I can't seem to get any of these working in the MAX Pack version of Carmageddon. Running windows 7, 32bit. Got the max pack, running the original Carmageddon in Hardware mode as it doesn't look quite as much like ass as the normal version does (SOOO MANY PIXELS D:).

I know you have to enter IWANTTOFIDDLE and IBETYOUCANTPRINTCUNT on the race menu, but when I do nothing happens. same with KEVWOZERE. No sound to show I've entered it, no clue as to what's happened, nothing.