Sega Rally 2

12 New Cars
When at the Title Screen, press Up, Down, Up, B, A, Left, B, B, Down.

Go into the 10 Year Championship and place 1st each year to unlock a new car.
Here is a list of the cars you get each year:
1  - Subaru Impreza 555
2  - Mitsubishi Lancer EVO 4
3  - Toyota Celica GT-Four ST-185
4  - Mitsubishi Lancer EVO 3
5  - Peugeot 106 Maxi
6  - Lancia Delta Integrale
7  - Fiat 131 Abarth
8  - Peugeot 205 Turbo
9  - Renault Alpine A110
10 - Lancia 037 Rally

After finishing in 7th place or better under the Easy difficulty setting, the Renault Maxi Megane is unlocked.
The Toyota Corolla Tien is unlocked after you highlight the Toyota Corolla on the Car Selection screen and hold L while selecting it

Fast Frame Rate
At the Title screen, press Up, A, Down, Down, Left, Right, B, B, Down. If done correctly, you'll hear a sound. The frame rate will now be set at 60fps. To have it set to 30fps, while you're at the title screen, press Up, A, Down, Down, Left, Right, B, B, Up

Get All Seasons
While at the Title screen, press Up, Left, Down, Right, B, A, B, Right, Down

Low Res Tracks
At the Track Selection or Mode Selection screen, press Y or R. If done correctly, the track will be less detailed and the race timer will be at the right side of the screen

Get Secret Rally Track
Complete the 10 Year Championship Mode, getting 1st place in every year

New Car Colors
At the Car Selection screen, press L

Camera Control
During a replay, press A, Y or X to change views and press B to return to the normal view. Press the D-Pad to control the camera at the Car Selection screen. For a behind the car view, press A