Karamjan rum (banana) is an item made by using a banana on a bottle of Karamjan rum. It serves no practical purpose.
Adding the banana gives the following message: You stuff the banana into the neck of the bottle. You begin to wonder why.
Unlike the regular rum, it can be taken off the island by teleporting. However the customs officers will confiscate it if the player has started Pirate's Treasure and attempts to charter a ship.
This item serves as a red herring in the quest Tai Bwo Wannai Trio, in which the player must use sliced banana with Karamjan rum. Many players forget to slice the banana first, forcing them to collect another Karamjan rum and banana.