Cheat Codes
Enter these in the cheat code console to get the extras!

getheadk= Pumpkin Heads
getheadj = Yellow Smile
R04r = Special move Roar
allin = Special move Zone
ontheroad = No damage
roadtrip = Unlock all cities
getheadl = Bunny ears
dfens = Special move Agro
getheadn = skull head
getheadm = snowman head
trythisathome = flaming head
haveyouseenthisboy = chrome body
crosscountry = All cities unlocked in arcade mode
urbansprawl = Faster pedestrians/All cities in arcade mode
hyperagro = Increase car mass in arcade mode

Unlockables
Complete the objectives to unlock the prizes

Mercedes SL55 AMG: Complete the San Diego Tournament after unlocking Detroit

Skully: Beat all the races for the Chopper of America Bike club to unlock a skully.

Race Starters as Riders: Find 36 hidden R* Collectables

R* License Plates: Find 24 hidden R* Collectables

Flag Vinyls: Find 12 hidden R* Collectables

Cadillac Sixteen: Get 100% Completion

Hotmatch Cuevito Motorcycle: Win all of Phil's 4 races in career mode.

Nissan Skyline: beat all 13 tuner race tournaments

El Diablo Rigid: beat vanessa three times in career mode

Lamborghini Murcielago: Complete U.S. Champs Series (After Beating Detroit)

Four-Twelve Complete all: 16 Exotic Races

Chrysler 300c dub edition: win balboa park tournament in san diego

Cadillac Escalade ext dub: edition + $10,000 win hotlanta tournament in atlanta

Mercedes cl 55 amg: Beat all the Luxury Races

68 Corvette Stingray: Beat All American Royalty races

1949 Chevy Fleetline: Win Bad Boyz Tournament in Detroit

Kawasaki Ninja ZX 12R: Beat all 14 Sports Bike Races

Vito Bike Rider Outfit: Beat Vito in San Diego

Phil Bike Rider Outfit: Beat Phil in San Diego

Naomi Bike Rider Outfit: Beat Naomi in Atlanta

Atlanta police cruiser: Beat all tournaments in Atlanta

San Diego police cruiser: Beat all tournaments in San Diego

Police Bike: Get 100% game completed

Spider Bike Rider Outfit: Beat Spider in Detroit

Kioshi Bike Rider Outfit: Beat Kioshi in Detroit

Car Rims Set 1: Beat Carlos in 3 of 3 Races in San Diego.

Flame Vinyls: Beat Bishop in 3 of 3 Races in San Diego.

Manufacture Vinyls & Car Rims Set 2: Beat Vanessa in 3 of 3 Races in San Diego.

Pearlescent Paint: Beat Vanessa the second time in 3 of 3 Races in San Diego.

Sportbike Rims: Beat Vito in 3 of 3 Races in Atlanta.

Tribal Vinyls & Car Rims Set 3: Beat Dre in 3 of 3 Races in Atlanta.

Color Shift Paint: Beat Roy in 4 of 4 Races in Atlanta.

Wild Vinyls: Beat Cheng in 3 of 3 Races in Atlanta.

Car Rims Set 4: Beat Lamont in 3 of 3 Races in Atlanta.

Chopper Rims: Beat Naomi in 3 of 3 Races in Atlanta.

Graphics Vinyls: Beat Roy the second time in 3 of 3 Races in Atlanta.

Chopper Vinyls: Beat Spider in 3 of 3 Races in Detriot.

Splash Vinyls: Beat Leo in 3 of 3 Races in Detriot.

Car Rims Set 5: Beat Roy in 3 of 3 Races in Detriot.

Sportbike Vinyls: Beat Kioshi in 3 of 3 Races in Detriot.

Car Rims Set 6: Beat Caesar in 3 of 3 Races in Detriot.

Car Rims Set 7: Beat Caesar the second in 3 of 3 Races in Detriot.

Tuner Exhausts: Race 1 of 13 from the Unbeatable Street Racing Club.

Tuner Tailgates: Race 2 of 13 from the Unbeatable Street Racing Club.

Zone for Tuners: Race 3 of 13 from the Unbeatable Street Racing Club.

Tuner Front Bumpers: Race 6 of 13 from the Unbeatable Street Racing Club.

Tuner Side Upgrades: Race 7 of 13 from the Unbeatable Street Racing Club.

Tuner Rear Bumpers: Race 8 of 13 from the Unbeatable Street Racing Club.

Tuner Hoods: Race 9 of 13 from the Unbeatable Street Racing Club.

Tuner Spoilers: Race 10 of 13 from the Unbeatable Street Racing Club.

Muscle Car Exhausts: Race 1 of 15 from the American Royalty Racing Club.

Roar for Muscle Cars: Race 3 of 15 from the American Royalty Racing Club.

Muscle Car Rear Upgrades: Race 5 of 15 from the American Royalty Racing Club.

Muscle Car Front Bumpers: Race 7 of 15 from the American Royalty Racing Club.

Muscle Car Side Upgrades: Race 9 of 15 from the American Royalty Racing Club.

Muscle Car Rear Bumpers: Race 11 of 15 from the American Royalty Racing Club.

Muscle Car Hoods: Race 13 of 15 from the American Royalty Racing Club.

Luxury Sedan Exhausts: Race 1 of 14 from the Luxury Rollers Racing Club.

Agro for Luxury Sedans & Zone for Sport Coupes: Race 3 of 14 from the Luxury Rollers Racing Club.

Luxury Sedan Front Bumpers: Race 5 of 14 from the Luxury Rollers Racing Club.

Luxury Sedan Side Upgrades: Race 7 of 14 from the Luxury Rollers Racing Club.

Luxury Sedan Rear Bumpers: Race 9 of 14 from the Luxury Rollers Racing Club.

Luxury Sedan Spoilers: Race 11 of 14 from the Luxury Rollers Racing Club.

SUV/Truck Exhausts: Race 1 of 15 from Big Playas Racing Club.

SUV/Truck Taillights: Race 2 of 15 from Big Playas Racing Club.

Agro for SUV/Truck: Race 3 of 15 from Big Playas Racing Club.

SUV/Truck Front Bumpers: Race 5 of 15 from Big Playas Racing Club.

SUV/Truck Side Upgrades: Race 6 of 15 from Big Playas Racing Club.

SUV/Truck Rear Bumpers: Race 7 of 15 from Big Playas Racing Club.

SUV/Truck Hoods: Race 10 of 15 from Big Playas Racing Club.

SUV/Truck Rear Upgrades: Race 11 of 15 from Big Playas Racing Club.

SUV/Truck Front Grills: Race 12 of 15 from Big Playas Racing Club.

Roar for Choppers: Race 3 of 15 from Choppers of America Racing Club.

Rider Outfits Set 1: Race 8 of 15 from Choppers of America Racing Club.

Chopper Vinyls: Race 12 of 15 from Choppers of America Racing Club.

Riders Skins: Race 1 of 14 from Original Riders Racing Club.

Zone for Sportbikes: Race 3 of 14 from Original Riders Racing Club.

Rider Outfits Set 2: Race 8 of 14 from Original Riders Racing Club.

Zone for Exotics: Race 3 of 16 from Invitation Only Racing Club.

'57 Chevy Bel Air: Lead the San Diego Stage Tournament in points (4 races).

Lexus IS300: Lead the San Diego City Tournament in points (3 races).

Ducati 999R: Lead the Hotlanta Tournament in points (3 races).

Cadillac Cien: Lead the Detroit City Tournament in points (3 races).

Free Neon
To get the red, green, blue, and white neon for free go to the neon menu and select "no neon" for $0 and exit the menu. When you go back to the menu the standard colors are all listed as "purchased"
DOES NOT WORK ON REMIX

Start In front of other racers before a race
To start in front of your opponents, you have to hold R1 and X and push left or right (depending on which racer you want to start in front of.) on the left analog stick so that you will move in a 180 degree motion, so that the rear end of your car hits the side of the other racers which helps put you in front of them. If done correctly, you will start the race exactly after you do this.
WILL NOT WORK WITH MOTORCYCLES

Wow! Great work, Slushy!

I merged the threads together and did some editing. Plenty of hints in there