Activate cheat mode (do this one first!):
Up, Down, Left, Right, Down, Right, L1, R1, R1

Blood Mode:
L1, Down, R1, Left, L1, Right, R1

Angels (when blood mode is activated):
Up, R1, Down, L1, Up

Immortal:
Left, R1, Up, L1, Up, Right, R1, Down, L1

Choose Mission:
Up, Down, Circle, L1, R1, L1, Circle, Down, Up

Next Mission:
Square, Circle, R1, L1, Circle, Down, L1, Up

Car Select:
Left, R1, Right, R1, Left, R1, Right, R1

Debug Mode:
Up, Right, Left, Down, Circle, L1, R1, R1, L1, Circle, Down, Left, Right, Up

Invulnerable:
L1, L1, L1, L1, Left, Circle, Circle, Square, L1

Infinite Fuel:
L1, Circle, Left, L1, Circle, R1, L1, Up, R1, Down

Car Tune-up:
L1, R1, L1, Up, Down, Circle, Down, Right, Left, Square, R1

Extra Nitro:
L1, Circle, Down, L1, Up, Square, Circle, R1

Add 1 minute to time:
Down, L1, L1, Circle, Circle, R1, Up, Square, L1

Extra Money:
L1, R1, Up, Circle, Down, Square, Right, R1, L1

Access All Time Trials:
R1, L1, Circle, Left, Circle, Circle, Left, L1, Circle.

Access NY Time Trial:
L1, Right, Down, Left, Up, R1.

Access Tokyo Time Trial:
L1, Left, Right, R1, Left, Right, L1.

Access Subway Time Trial:
L1, Left, L1, R1, Right, R1.

GameShark Codes

Infinite Armor		800a86a00800

 
Infinite Fuel		800a7e100064

 
Infinite Heavy Homers	800a5ebe0063

 
Infinite Heavy Mines	800a5eae0063

 
Infinite Heavy Rockets	800a5eba0063

 
Infinite Heavy Swarmers	800a5ec20063

 
Infinite Homers		800a5ebc0063

 
Infinite Medium Rockets	800a5eb80063

 
Infinite Mines		800a5eac0063

 
Infinite Oil		800a5eb00063

  
Infinite Oil Slick	800a5eb20063

 
Infinite Rockets	800a5eb60063

 
Infinite Swarmers	800a5ec00063

Thanks to Revolution readers Headilious Munch, Powerkid5, Bully32, Ryan Carroll, Jonathan Liles, Rebel and Crasherone!