Time Crisis II:
Automatic weapons: 
Beat story mode twice to unlock automatic weapons. 

Crisis mission mode: 
Beat story mode once.

Free play mode: 
Every time the player uses all credits in the story mode, a credit is added to the total available. After nine credits, the credits change to free play mode.

Infinite ammunition: 
Complete story mode using automatic weapons.

Mirror mode: 
Complete story mode using only one credit. 

Music test: 
Complete crisis mission mode. This also unlocks Final Mission 2.

Shoot Away 2 extra mode: 
Achieve a high score in Shoot Away 2 retro mode.

Wide ammunition: 
Complete story mode using infinite ammunition.

Stage 1 Bonus:
Shoot the boss's hat all four times and you'll be treated to an area where there is nothing but yellow bonus enemies. 

Stage 2 Bonus:
On stage 2-2 shoot the two bonus enemies when the train goes past you. You will take the other route with some bonus enemies. 

Stage 3 Bonus:
This only works in Solo mode. When fighting Wild Dog for the first time, shoot him as many times as possible. If you hit him enough times, in the scene where the agents attack him from both sides, yellow bonus soldiers will appear instead of the regular gray and white soldiers.