iammostwanted - Unlocked cars
givemethegto - Releases the GTO
iammostwanted - Unlocks all cars
burgerking - Unlocks Burger King Challenge
castrol - Unlocks Castrol Ford GT
10,000:
To an extra 10,000 in career mode have a Need For Speed Underground career game saved on your hard drive. After the prologue you will get 10,000.
Quick start:
Pay close attention to your tachometer when launching from the start line. Grab a perfect launch to gain a few precious seconds. When the needle turns blue drop the clutch and hold on.
Nitrous and grip:
Hitting nitrous torques the chassis back, giving the rear tires immensely more weight under the new acceleration. The end effect is that you will go straight. If you find your tail sliding out or are about to spin out of control, hit your nitrous. You will be surprised at how fast you will get straight again. This is a great trick in combination with Speedbreaker. With the correct timing, there is no corner you cannot take at any speed.
Special Marker:
Enter at title screen: up,up,down,down,left,right,up,down
You will be able to use in the Backroom of the One Stop Shop
Easy money:
If you are low on cash, just defeat one of the opponents on the black-list. You will get two marks to use on several different things. Do not use them on the Uniques early in the game. Instead, use them on the middle or the left "Random" choices. They should always come out to either be a big cash bonus or the opponent's pink slip.
Recommended car:
The best start car is the Cobalt SS. Use that car until you get the Eclipse. When you win blacklist races, try for the three "?" markers. You can get cash or the pink slip car. If you get their car, go to the safe house and sell it. You can get good money by doing this, and get unique upgrades after you start getting into the visuals after you switch from the Cobalt.