Resident Evil 2 Dual Shock

Unlimited Ammo

During a game press select to go to the options screen. Go to Key Configuration and highlight Configuration A and hold R1 and press square 10 times. The word manual will turn red. You can also do this code in Extreme Battle, Hunk, and Tofu's games.

Play as Chris and Ada

First you have to beat the game on "origional" mode. Then beat scenario B will an A ranking and you will get to play a new scenario called "Extreme Battle" where you have to get to the Police Precinct and find four bombs. Beat that and you will get Ada as a character. Beat it with her and you will get to play as Chris Redfield from the first Resident Evil.
(this only works with the Dual Shock Edition)