2000 Plastic
Enter the following cheat in the middle of gameplay (you will hear a foghorn if entered correctly):

While Holding R2: press triangle, square, O, X, triangle, X.

5000 Plastic
Enter the following cheat in the middle of gameplay (you will hear a foghorn if entered correctly):

While Holding R2, press triangle, O, square, X, triangle, square.

Suicide
Enter the following cheat in the middle of gameplay (you will hear a foghorn if entered correctly):

During gameplay, hold R2, then press square, triangle, left, left, triangle, square. You will hear a foghorn when entered correctly.

Other Codes
Enter the following cheat in the middle of gameplay (you will hear a foghorn if entered correctly):

STSSXO - Randomly change the colors of the teams on the map
TOSXTS - Get 5000 plastic
SSXTXS - Super strong player team
TTXSTT - Super strong enemy team
OSOSTT - Drop some paratroopers
SSSTOX - Get lots of resource from dumptrucks
TSOXTX - Get 2000 energy
STLLTS - Get a suprise!

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