Play as Kraken:
Beat the game with all eight characters to unlock Kraken.

Play as Valgas:
Beat the game with Kraken to unlock Valgas.

Play as Final Valgas:
Beat the game with Valgas on difficulty level 8. Enter page 12 of the Power Stone Collection to see Final Valgas. Final Valgas may only be selected in Vs. mode, by only one player per match.

Extra Options:
Beat Arcade mode with any character on any difficulty level.

Virtua Battle Mode:
Unlock Valgas as a playable character. Virtua Battle Mode will now be available on page 5 in the Power Stone Collection.

Dual Virtua Battle Mode:
Beat the game with Valgas to unlock this mode on page 6 in the Power Stone Collection.

Bonus items:
Beat the game using four characters to unlock a shield, heavy chain gun, ray gun, and extending pole.

Scrap book:
Accumulate 1000 or more coins in the VMS mini-games to unlock a scrap book option on page 13 in the Power Stone Collection.

Sound test:
Accumulate 2000 or more coins in the VMS mini-games to unlock a sound test option on page 25 in the Power Stone Collection.

See ending sequences:
Beat the game to access page 14 in the Power Stone Collection..

Change victory view:
At the end of a match, press the D-pad or Analog-stick to change the viewing angle and press A to move the camera in, release A to move the camera out.

Last Boss:
To beat the last boss just go under his right leg where he can't hit you.

GameShark Codes

P1 Play As Final Valgas 5DD76E930000000A
 
P1 Play As Kraken     5DD76E930000000C
 
P1 Play As Valgas     a610ee2200000009
                      5DD76E9300000009 
 
Infinite Power Up Energy P1
                      28277AE600000938
 
 
No Power Up Energy P1 28277AE600000000
 
50% Power Up Energy P1
                      28247AE6C0704F66
                      28277AE60000049C
 
Infinite Power Up Energy P2
                      9A68133100000938
 
 
No Power Up Energy P2 9A68133100000000
                
50% Power Up Energy P2
                      9A6B1331C0704F66
                      9A6813310000049C
 
Have No Stones P2     A543485700000000

Have All Stones P2    A543485700000707

Infinite Health P1    E8070137000000F0

Low Health P1         E8040137C070503F
                      E807013700000000

50% Health P1         E8040137C070503F
                      E807013700000078

Low Health P2         7E26CAC4C070503F
                      7E25CAC400000000

Infinite Health P2    7E25CAC4000000F0

50% Health P2         7E26CAC4C070503F
                      7E25CAC400000078

Have All Stones P1    36813DE400000707

Have No Stones P1     36813DE400000000
 

Thanks to Revolution readers Kevin and Stuart Tosney!