Cheating in Ultima III

Ultima III is the first of the series in which cheating is possible. The game does not have internal cheating options, but there are several features that can be abused due to oversights in programming.

Exotics: Armor and Weapons
Exotic Weapons and Exotic Armour can be used to obtain a virtually infinite amount of money. These weapons and armour are found by digging in particular locations, and can be later sold to a merchant. After doing this another set can be obtained by digging again in the same location. This can be repeated over and over again in order to obtain as much money as desired. (Note that this method may not work in all ports of Ultima III, including the Apple and PC versions, where merchants only accept items they sell.)

Money Galore
You can enter the Dungeon of Doom, go east five steps through the secret door, grab the chest (preferably with Appar Unem), return to the ladder, exit and then repeat.

Easy Entrance to Exodus Castle
The way that pirate ships are spawned in Ultima III after reaching level 5 can be used to get to Exodus earlier than expected by the plot. Entering the moongate that leads to the Isle of Fire often gives the chance that a pirate ship is spawned in the small pool of water behind the Great Earth Serpent. This ship allows easy access to the castle from the moongate, making the journey into the Dungeon of the Snake no longer needed. The ship is also safe from the whirlpool behind the serpent.

Free Horses
Horses cost 800 gold pieces, and though they can be found for free in Old Fawn, they can't be taken out of it since it is on an island and horses can't board ships. However, using three ships as a bridge between the island and the mainland allows riding the horses onto the mainland and parking them there. This can be done as often as wished, as long as the ships aren't eaten up by the whirlpool.

Dag Acron
In the IBM-PC port, the mage-spell Dag Acron also works while sailing a frigate, teleporting to another water tile. This can actually be used to bypass the Great Earth Serpent, thus negating the need to get the Mark of Snakes.

Shortcut to the Endgame
The NES port has a bug that can short-circuit the plot. The Four Cards aren't actually needed; it is enough to make it to Exodus himself. This can be done the quick way just by misusing the Moongate to the Isle of Fire until a pirate ship spawns in the small pond behind the snake, enabling access to the castle without the need for the Mark of Snakes. Once Exodus has been reached, the game will behave as if the player already has all four cards, even if they really don't.