Top Gear Rally cheats and cheat codes for Nintendo 64

Unlock cars and tracks:
Go to the arcade mode screen and press the following button combinations:

All tracks: Press A, Left, Left, Right, Down, Z.
All cars (except bonus cars): Press A, Left, Left, C-Down, A, Right, Z.
Beach ball car: Press B, B, A, Left, Left, C-Down, A, Right.
Cupra car: Press C-Down, Up, B, Right, A, C-Down, A, Right. 
Helmet car: Press Up, Up, Z, B, A, Left, Left.

Black or white cars:
Highlight a car at the car selection screen, then 
hold L + R + C-Up + C-Down + C-Left + C-Right, and press Up or Down.

Change car color:
At the car selection screen hold the following buttons:

Red - Hold C-Left 
Blue - Hold  C-Right
Green - Hold C-Up
then press Up or Down.

Mirror finish cars
Hit C-Down after completing all six seasons of year five.

Rainbow mode
During game play, hit C-Down, Z, B, Up, Up, Right.

Disable Bi-linear filtering
During game play, hit B, Left, Right, Up, Left, Z, Right.

New credits screen:
Select the "Credits" icon at the options screen. After, hit 
Left, C-Down, Right, Down, Z.