.69 Ferguson Rifle:
Never let Reed out of your sight. If he is by himself and you cannot see him, he gains life.
Desecrate Hoodoo's corpse:
After you defeat Hoodoo, there will be a intermission sequence showing him dead standing up in a coffin. After the sequence, he will still be in west empire standing in the grave. You can take out your double-barrel shotgun and shoot him a few times in some areas. You can shoot off his head, arm, and both of his legs. leaving a corpse floating in an up-right coffin.
You can make more money on the bounty hunter side missions by capturing bounties alive. When you find a wanted poster that offers more money if you capture them alive and are having trouble doing so, use the following trick. Kill all gang members or bodyguards (if any). If the bounty is on a horse, kill the horse. Get close and melee attack. This will stun the fugitive and present an opportunity to grab them. Then, subdue the fugitive. This awards you more money for each bounty. If you accidentally release him, you can try to melee him and grab him again. However, if you do this too many times or if he has been shot, you may kill him and get less money.
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.
End of poker cheating:
When playing Texas Hold 'em after the tournaments in the Alhambra, you will no longer have the option of cheating.
Hold [Dash] while repeatedly jumping your horse to travel about double the speed.
If you scared off the quarry in the Hunt side-missions, just remember where it was and go to the nearest trader. After you talk to him and return to where the animal disappeared, it will be there again.
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.
Unlock Apache shirt:
Successfully complete Hunting to unlock the Apache shirt.
Unlock silver spurs:
Successfully complete Pony Express to unlock silver spurs.
Unlock various stuff:
Successfully complete story mode to unlock Reed's armored horse, Magruder's seven barrel Nock gun, and the Cannon Nock gun.