Enter the options menu and select "Gameplay". Hold D-pad Left + Left Analog-stick Right and press Start. The "Codes" selection will now be unlocked at the options menu.
Bonus teams
Enter "MEGASTARS" as a case-sensitive code to unlock the Sega Sports, Visual Concepts, and Team 2K2 in exhibition and street modes.
Play as a Legends team in season mode
Go to season mode and edit the season. Take out any team and put in the Legends team.
Easy three pointers with Allen Iverson
Choose Allen Iverson and go to the left side of the court near the corner. If a defender is checking you, upfake. When he flies away trying to block your shot, shoot the three pointer. The release must be excellent. After shooting two or three of them, he will become hot.
Easy win
Turn off fouling in the NBA rules section of the options menu. Use the intentional foul to make the other team drop the ball, pick it up, score, and repeat as needed. Turn off fouls and goaltending then just keep blocking them and there will be no foul.
Easy dunk
To do the Vince Carter dunk (under the legs) on a break away, control Stackhouse, Bryant, Carter, Macgrady, or any other good player. Hold Turbo and go up for a dunk. You will make it most of the time.