Dead To Rights

Stage selection:
Push Up, Down, Up, Down, Left, Right, Right, Y, X, X buttons on your
controller while you are at the main menu (you should see the new game
option). If the code is accepted, you should hear a scream. Push Down
at the "Press Start" screen until you will see the level selection
option.

Unlock Mini-games
Finish the game once on any difficulty level to get access to the
hidden mini-games.

Disarms
Each weapon have a 5 disarms:
Up + B
Right + B
Left + B
Down + B
and B

Except shotgun: B and Up + B.

Boomstick mode:
On the "New Game" screen, hold L + R and push Y, X, Up, Up, Up buttons
on your controller to unlock unlimited shotgun. If the code is accepted,
you should see a message.