Paired Gauntlets of Striking

These leather gloves are reinforced with steel plates and decorated with images of two humanoids fighting side-by-side. While you and another creature are each wearing one of the gauntlets and are each within 5 feet of the same creature, you both have advantage on the first attack roll you make against that creature on each of your turns.

Source: Tome of Heroes · OGL-1.0a · 5.1