For most users, NFS MW Save Editor v1.3.5 (by nfs-modders) offers the best balance of safety and features.

: This is the most comprehensive tool for "extra quality." It allows you to unlock all cars and parts by pressing F5 in the main menu. It also enables features like a 100-car car lot for new save games and the ability to use bonus cars (like the BMW M3 GTR) in Career Mode.

Look for a button or tab labeled or "Unlock All." In v1.3.5:

To add the legendary Undercover Police Corvette (C6) (which is faster than any racer car when upgraded):

Using a save editor involves: