Gun

Faster riding:
Hold (Dash) while repeatedly jumping your horse to travel about double the speed.

Unlock Magruder's seven barrel Nock gun:
Successfully complete story mode to unlock Magruder's seven barrel Nock gun.

Unlock .69 Ferguson Rifle:
Defeat Hollister.

Unlock Apache Shirt:
Successfully complete the Hunting missions..

Unlock Dual Peacemakers:
Defeat Reed.

Unlock Silver Spurs:
Successfully complete the Pony Express missions.