Ambidextrous people have the ability to use both hands with equal dexterity. But the ambidextrous probably prefer to write with their right hands, since lefties always smudge what they've written as they drag their hand across the page.
Coming from the Latin word ambidexter, which means “right-handed on both sides,” ambidextrous describes someone who can use either hand to write, swing a bat or catch a ball. Lucky ducks. In a broader sense ambidextrous means "facile" or "skillful." But when it first came into use in the 1530's, ambidextrous had more sinister connotations with the practice of deceitful double-dealing.