Running Shirt

A Running Shirt is a Shirt available in Golden Sun and Golden Sun: The Lost Age.

Basic Description
It can be won as a prize at the Lucky Wheels slot machines, located in Tolbi in Golden Sun and in Contigo in The Lost Age, and therefore multiple Running Shirts can be obtained.

The Running Shirt increases the wearer's defense by 1 and agility by 15. Obviously, it should be equipped for its agility increase, rather than defense. It can be bought for 400 coins and sold for 300 coins, making it the least physically-valued Shirt available.

Analysis
Don't let its low item value and Defense fool you, this is an immensely useful piece of supplemental equipment in both Golden Sun games, providing a substantial boost to the Agility rating of any Adept you please without taking up any of the established equipment slots. With it, you can make a healer like Mia more capable of performing her healing before the enemy commences its attack, make Garet much less slow (assuming you're playing him in his Guard class series), and so on, and its Agility-boosting effect stacks very well with the even stronger Quick Boots item that can also be won in Lucky Wheels. It is very likely that an endgame party in both games would want at least several of its Adepts equipped with this.

There is an alternative to consider over the Running Shirt, though, and that is the Mythril Shirt, also won in Lucky Wheels, which provides a nice boost to overall durability. It and the unique shirt that is its effective enhanced form in The Lost Age, the Golden Shirt, is much better to equip on an Adept that has high Agility but low durability, and Ivan and Sheba fit this bill perfectly.