Mad Dog II: The Lost Gold

Story-related and unmissable.

Just need to beat Mad Dog. You have unlimited continues, and continues pick up at last checkpoint. The only real challenge in beating the game is that the final town requires 27 kills (and avoiding 3 or 4 innocents) with no checkpoints. Get used to hearing the Monk's Warning numerous times. After the town, beat Mad Dog in a Quick-Draw Showdown. Just as in Mad Dog McCree, you'll need to aim specifically for his hand to disarm him, then shoot him again in the head when he tries to pull out his back-up pistol (you can't shoot him again until he tries to draw on you).