Irish Claddagh Ring
The Irish are best known for the Claddagh Ring. This was given to the woman as a sign of faith and love by the man when he went away for a while - perhaps to war, perhaps to the New World to make his fortune. There is some confusion about the ring being worn certain ways when the woman is not taken. That's not the point of the ring - the point is that it's worn because the woman IS taken.
You can make the ring even more personal by using the birthstone of the person, so it's clearly For Her or For Him.
The Claddagh Ring
Irish Wedding Traditions