Enter the following codes at the 'Load Game' screen to unlock the corresponding effect. If you have entered the code correctly you will be returned to the 'Main' menu.

Unlock Unlimited Ammo:
Press Up(4 times), Right(4 times), L, R, L, R, C-Right, C-Left.

Unlock Invincibility:
Press Down(4 times), Left(4 times), L, R(2), L, C-Up, C-Down.

Unlock Hunk as a Playable Character:
Press Up, Down, Left, Right, Left(2 times), Right(2 times), L, R, C-Up, C-Right, C-Down, C-Left.

Unlock Tofu as a Playable Character:
Press Up, Down, Left, Right, Left(2 times), Right(2 times), L, R, C-Up, C-Left, C-Down, C-Right.

Secret Film
First get to the police station, then go up to STAR's main office on the second floor. From there click on the desk - you may have to fo this about 50-75 times. You persistance should then be rewarded and you will receive a film which can be developed.