God mode:
During play, press A, Y, X, X, Y, Y, B, Y, X, A.

50 Skill Points:
During play, press A, B, Y, X, Y, B, B, Y, B, A.

100,000 Gold:
During play, press A, X, Y, B, Y, B, X, B, B, A.

Neutral Rep:
During play, press A, X, Y, X, Y, B, B, Y, B, A.

Improving your relations with nations:
To improve your relations with hostile nations, go to Quebradas Costillas' tavern. A man sitting in the corner will ask you what nation to improve relations with - for a price, of course. This will help afterwards with those fort conquering expeditions.

Thanks to Revolution readers Juicy Fruit and Sentry Robot!