Change Nick's Appearance:
When naming your game file (when you are making your license plate), put in the following names. Hold L1 and R1 when you enter and confirm the name.
Look like the Chief - B1G1
Look like Rosie - ROSA
Look like Rosie in lingerie (like in the Blood Money episode) - HURT_M3
Look like a cop - FUZZ
Look like a police officer - FATT
Look like a SWAT officer - 5WAT (alternate code - SWAT)
Look like a commando - M1K3
Look like a female worker - HARA
Look like a male worker - HARA
Look like a female punk - B00B
Look like a male punk - MNKY
Look like a gangster - TFAN
Look like a boxer - BRUZ
Look like a gambler - MRFU
Look like a butcher - PHAM
Look like a biker - HAWG
Look like a S&M donkey - JASS
Look like Ancient Wu's concubine - TATS
Look like a pimp - P1MP (alternate code - PIMP)
Look like a hobo - B00Z
Look like a corpse - J1MM

Cheat Codes:
On the map screen, press the following:
Get all moves, cars, and weapon parts - UP, RIGHT, DOWN, LEFT, UP, A
Get all melee combat skills - UP, DOWN, UP, DOWN, A
Get all driving skills - LEFT, RIGHT, LEFT, RIGHT, A
Get all gun skills - RIGHT, LEFT, RIGHT, LEFT, A
Increase car size (must be inside a car first) - DOWN, DOWN, DOWN, A
Display Nick's position - A, X, B, Y

Unlock Bonus Movie:
To unlock the bonus movie, get all three endings (poor, average, and best) by successfully passing all of the episodes, including the alternate ones. This extra movie is just for fun, and it shows Masterson and Nick doing something silly at the Gulag Club.

Unlock Snoop Dogg:
On the map screen, press R, L, UP, RIGHT, LEFT, DOWN, Z, Z, A, Y, X, Y. You should hear a chime to confirm that you did it correctly. Now, go to a place that will save your game. Then, go to the Mission Select Screen and pick a mission that shows Snoop's head to play as him.

Hint: Change Nick's Car Color:
When making a license plate, hold L + R and press DOWN and UP to cycle through all the colors. (The color of the horizontal bar represents the color the car will have.)

Hint: Dealing With Criminals on the Street:
When dealing with street crimes, use the siren, wave your badge, or fire warning shots to try persuading the enemies to stop fleeing and surrender.

Hint: Quick And Easy Good Cop Points:
If you want to earn good cop points quickly, go to a street called Rose Ave. in Venice. All of the people walking on that street are usually either carrying drugs or guns. Simply walk up to anyone on that street and frisk them and you'll bust them. (Rose Ave. is the street by the beach and in directly on the "N" in the title Venice on the map; you can look up the map from the start menu).

Hint: Unlimited ammo:
You can exploit a game bug to effectively give Kang unlimited ammo with a gun of your choice. This trick will only work in the free-roam missions, as other missions won't allow you to holster your gun as the trick requires.

Pick up the gun for which you'd like unlimited ammo, and then pick up a secong gun to move the first gun to Nick's right hand. When your right-handed gun is low on ammunition, holster your guns and press R1 + R2 to fire a shot into the air (just once). Unholster your weapons and the right-handed weapon should have a full clip of ammo. Repeat the trick as necessary.