Press Up, X, X, Down, Left, X, X, Right during game play. The chainsaw, grenades, revolver, SMG, combat shotgun, mini-gun, and sniper rifle will be unlocked. A message will confirm correct code entry. To get unlimited ammunition for this or the other weapons tiers, repeatedly enable the code until no ammunition number appears beneath the gun pictures. Enabling this code will cause your street creds to substantially drop in points.