Invincibility
     At  the  Press  Start  screen,  press  A, Z, Z, Up, Left, C-Left,
C-Left,  C-Down. If done correctly, a message saying "Invincible" will
appear on the screen.

Level Select and Battle Mode
     At  the  Press Start screen, press A, R, Z, Up, Up, C-Up, C-Down,
C-Down.  If  done  correctly,  a  message  saying "Missions Open" will
appear on the screen.

Skip Credits
     Reset the Nintendo 64 after the opening credits start.

Infinite Primary Weapon
     At the Main Menu, press A, R, Z, Right, C-Up, C-Right, C-Down, 
C-Down.

Infinite Solaris Missiles
     At the Main Menu, press B, L, L, Z, Up, Down, C-Up, C-Up.

Infinite Titans
     At the Main Menu, press A, B, L, Up, Up, C-Up, C-Up, C-Right.

Freeze Enemies
     At the Main Menu, press R, Z, Right, Right, C-Up, C-Left, 
C-Right.

One-Hit Kills
     At the Main Menu, press B, B, B, L, R, Left, Down, Down.

Stealth Mode
     At the Main Menu, press Up, Up, Up, Up, Right, Down, C-Left, 
C-Left.