Completion bonuses
Successfully complete story mode to unlock Magruder's seven barrel Nock gun.
Successfully complete story mode and all side missions (100% completion) to unlock Reed's armored horse and Magruder's Cannon Nock gun.
.69 Ferguson Rifle
Defeat Hollister.
Apache Shirt
Successfully complete the Hunting missions.
Cavalry Sword
Defeat Reed.
Dual Peacemakers
Defeat Reed.
Silver Spurs
Successfully complete the Pony Express missions.
Unlimited ammunition
Take a barrel of TNT from the Badlands mine. Find the abandoned house in the Badlands where the buffalo graze. Go to the back of the house on the outside. Face the chimney (looking west) and place the TNT barrel on the left side of the chimney. Blow up the TNT barrel to open a hole in the ground with unlimited ammunition for all weapons.
New Game +
Complete the game and return to the starting area (Blackfoot Territory). From the LEFT of the HIGHER boulder leading up to a ledge and gap, jump and spur your horse so it lands on top, then onto the ledge. Cross the next two areas. Stand between the only two rocks in the water. Press and hold LB+LT+RB+RT+A for a few seconds until you hear a strange sound. Go to Options (press [Start]),for a new selection - GUN. Choose any Mission or Cutscene. You will retain ALL weapons, items, and skills.