Rusty item
Rusty items are a small class of items introduced in Golden Sun: The Lost Age. They are unique weapons that are extremely weak when first found, but if you have Sunshine the blacksmith in Yallam take a look at a rusty item he will offer to reforge it into the rare weapon artifact it's meant to be. If you do, he will take it and will be done as soon as you leave and reenter the town, at which point his wife will give it to you, for a price of course (though in the English version of the game the price is not stated).
They return in Golden Sun: Dark Dawn, where they are instead forged by Obaba in Champa. The forging process is mostly identical between the two games; however, Obaba does not charge the player, instead giving the forged equipment for free.
Long Swords
Robber's Blade: An Artifact that increases base Attack by 101. Its Unleash effect, Shred, is an attack that adds 33 damage, is based on the Mars element, and may lower the target's Defense rating by 25%. It is obtained in Golden Sun: The Lost Age, and it is found in a treasure chest in Aqua Rock. Its buy value is 7600 coins and its sell value is 5700.
Soul Brand: An Artifact that increases base Attack by 141. Its Unleash effect, Soul Shatter, is an attack that adds 50 damage, is based on the Mars element, and 10% of the damage done is added to the user's own PP meter. It is found out in the Great Western Sea while sailing, at the southern of the two shallow spots west of Atteka. It is obtained in Golden Sun: The Lost Age, and it is surrounded by a ring of rocks that requires the ship to have the Wings of Anemos attached so it can fly over into it. Its buy value is 11600 coins and its sell value is 8700.
Rune Blade: An Artifact that increases base attack by 162. It has three Unleashes: Life Nourish, Vorpal Slash, and Void Beam. Life Nourish is an attack that adds 25 damage, is based on the Venus element, and may heal the wielder by the damage dealt. Vorpal Slash adds 16 damage, is Jupiter based, and has a range of 3 adjacent targets. Void Beam adds 57 damage, is Jupiter based, and may seal the target's Psynergy. It is obtained in Golden Sun: Dark Dawn, and it is found south of Yamata and east of the group of islands. While rusty, it can be bought for 720 coins and sold for 540 coins. After being reforged, it can be bought for 15000 coins and sold for 11250 coins.
Light Blades
Corsair's Edge: An Artifact that increases base Attack by 90. Its Unleash effect, Lunar Slash, is an attack that adds 25 damage, is based on the Jupiter element, and may lower the target's Resistances by 40. It is found in Lemuria by digging it out of a spot on the ground using the Scoop Psynergy. Its buy value is 6300 and its sell value is 4275.
Pirate's Sabre: An Artifact that increases base Attack by 136. Its Unleash effect, Scorpionfish, is an attack that adds 43 damage, is based on the Mars element, and may inflict Venom on the target. It is found out in the Great Western Sea while sailing, when searching a shallow spot immediately southwest of Osenia. Its buy value is 10600 and its sell value is 7950.
Kikuichimonji: An artifact that increases base attack by 128. It has three Unleashes: Combat Dance, Zenith Strike, and Asura. Combat Dance multiplies damage by 1.5, and is non-elemental. Zenith Strike adds 59 damage, and is based on the Jupiter element. Asura adds 64 damage, is based on the Jupiter element, has a range of 3 adjacent targets, and may ignore 50% of the target(s) Defense. It is found south of Champa, slightly northwest of the Crossbone Isle whirlpool. While rusty, it can be bought for 620 coins and sold for 465 coins. After being reforged, it can be bought for 13400 coins and sold for 10050 coins.
Axes
Captain's Axe: An Artifact that increases base Attack by 95. It does not have an Unleash effect; rather, it can be used as an item while in the inventory of an Adept that is able to equip it (but it does not necessarily have to be actually equipped) to increase an Adept's Defense rating by 25% in battle, though there is a chance its functionality as a Usable item will break and it will have to be repaired to reuse its Use effect. It is found out in the Great Eastern Sea while sailing, at a shallow spot shortly south of the foggy Sea of Time. Its buy value is 6800 and its sell value is 5100, its sell value while broken is 3400, and its repair value is 1700.
Viking Axe: An Artifact that increases base Attack by 137. Its Unleash effect, Stun Bolt, is an attack that adds 47 damage, is based on the Jupiter element, and may Stun the target. It is found in a chest in the earlier portion of Treasure Isle, in an area that becomes accessible once Felix gains the Grind Psynergy in Lemuria. Its buy value is 11000 and its sell value is 8250.
Maces
Hagbone Mace: An Artifact that increases base Attack by 108. Its Unleash effect, Wyrd Curse, is an attack that adds 41 damage, is based on the Venus element, and may Haunt the target. It is found out in the Great Eastern Sea while sailing, at a shallow spot a short ways east of Treasure Isle. Its buy value is 8400 and its sell value is 6300.
Demon Mace: An Artifact that increases base Attack by 115. Its Unleash effect, Evil Eye, is an attack that adds 38 damage, is based on the Venus element, and may inflict Delusion on the target. It is found in the interior portion of Gaia Rock, at the part where there is a long series of one-room multi-exit hallways. Its buy value is 9200 and its sell value is 6900.
Thanatos Mace: An artifact that increases base attack by 125. It has three Unleashes: Critical Strike, Fearless Attack, and Heartbreak. Critical Strike multiplies damage by 1.5 and is non-elemental. Fearless Attack multiplies damage by 1.7 and is non-elemental. Heartbreak adds 42 damage, is Venus-based, and may automatically Down the target. It is found west of Harun Village, and southeast of the Lost Ship. While rusty, it can be bought for 490 coins and sold for 367 coins. After being reforged, it can be bought for 10400 coins and sold for 7800 coins.
Staffs
Dracomace: An Artifact that increases base Attack by 128. Its Unleash effect, Aging Gas, is an attack that adds 45 damage, is based on the Jupiter element, and may add all damage done by the attack to the user's own HP meter. It is found as a rusty staff in the earlier portion of Islet Cave that does not require using the Teleport Psynergy to fully explore. Its buy value is 10700 and its sell value is 8025.
Goblin's Rod: An Artifact that increases base Attack by 134. Its Unleash effect, Sargasso, is an attack that adds 39 damage, is based on the Mercury element, and may instantly fell the target. It is found in a shallow spot in the Great Western Sea, northwest of Hesperia. Its buy value is 9800 and its sell value is 7350.
Glower Staff: An Artifact that increases base Attack by 126. Its Unleash effect, Flash Force, is an attack that adds 44 damage, is based on the Mercury element, and may seal the target's Psynergy. It is found in the Shrine of the Sea God dungeon, in the portion accessible with the Frost Psynergy. Its buy value is 10100 and its sell value is 7575.
Bows
Sagittarius Bow: An artifact that increases base attack by 170. It has three Unleashes: Triple Burst, Star Dust, and Blue Comet. Triple Burst multiplies damage by 1.8, and is Jupiter-based. Star Dust multiplies damage by 1.4, is Mars-based, and will strike up to five adjacent targets. Blue Comet multiplies damage by 2.2, and is Mercury-based. It is found on Basement 9 of Crossbone Isle. While rusty, it can be bought for 700 coins and sold for 525 coins. After being reforged, it can be bought for 29000 coins and sold for 21750 coins.