Need For Speed 6

Result Command Line Parameter
Car is invisible to others +ghost
Cops only use helicopters +helicoptersOnly
Disable confirmations +nofrustration
Disable movie demos +nomovie
Disable music +nomusic
Disable sound effects +nosnd
Disable reverberation +noreverb
Disable on screen displays +nofrontend
Disable mipmapping. +nomipmap
Disable particle animations. +noparticles
Enable main menu +minfront
Enable screen shots +screenshots
Enter locked events in event trees +opentree

Cheap chars

Note: This procedure involves editing a game file; create a backup copy of the file before proceeding. Use a text editor to edit the "cars.ini" file in the "cars" sub-folder in the game directory. Change the values after the "price=" and "nfsprice=" lines to "10". You can now buy all cars for $10 each.
Faster cars

Note: This procedure involves editing a game file; create a backup copy of the file before proceeding. Use a text editor to edit the "cars.ini" file in the "cars" sub-folder in the game directory. Change the "mass=" value to "100" for a faster car.

Open the folder of a powerful car, such as the F1, F50, etc. Copy the "car.ini" file from here and paste it over the original "car.ini" file of a slower car in its own folder (for example, the Elise). This instantly gives that car the speed and handling characteristics of the better vehicle. Note: Back up the original "car.ini" file of the slower car in the event that you want to revert it back to its standard settings.
Dodge Viper GTS

Get 2 million points to unlock the NFS edition of the Dodge Viper GTS.
Ferrari F50

Lead a single race, full grid, advanced, for eight laps to unlock the NFS edition of the Ferrari F50.
Lamborgini Diablo 6.0 VT

Get 2.5 million points to unlock the NFS edition of the Lamborghini Diablo.
Lamborghini Murcielago

Get 3 million points to unlock the NFS edition of the Lamborghini Murcielago.
McLaren F1

Get 4 million points to unlock the NFS edition of the McLaren F1.
McLaren F1 LM

Get 5 million points or win the World Championship to unlock the NFS edition of the McLaren F1 LM.
Mercedes CLK GTR

Get 4.5 million points to unlock the NFS edition of the Mercedes CLK GTR.
Porsche 911 Turbo

Get 800,000 points to unlock the NFS edition of the Porsche 911 Turbo.
Porsche Carrera GT

Get 3.5 million points to unlock the NFS edition of the Porsche Carrera GT.
Ford Crown Victoria

Successfully complete Hot Pursuit Event 5.
Vauxhall VX220

Win a single race in any mode with a first place position in all laps.