Successfully complete story mode to unlock Reed's armored horse, Magruder's seven barrel Nock gun, and the Cannon Nock gun.
Successfully complete Pony Express to unlock silver spurs.
Successfully complete Hunting to unlock the Apache shirt.
.69 Ferguson Rifle
Successfully complete the Hunting missions.
Easy poker game wins
When you are playing Texas Hold 'em inside the Alhambra, you can easily win with or without a good hand. Raise the bid to the maximum. This should make at least one to three players fold. You can then cheat to make your hand better, and if it is a worse card, forget about the cheat card and go back to your original hand. Afterwards, keep checking your hands until one of you wins. It should be you most of the time. Do not worry if you lose; the tournaments are free.
Successfully complete the Pony Express missions.