Stylus

The stylus is a pen-like object for use with the touch screen on the Nintendo DS and Nintendo 3DS.

To date, the Legend of Zelda games that use the stylus are Phantom Hourglass, Spirit Tracks, Four Swords: Anniversary Edition and Ocarina of Time 3D. The 3DS Virtual Console versions of The Legend of Zelda, The Adventure of Link, The Legend of Zelda: Link's Awakening DX, and The Minish Cap require the stylus to operate several Virtual Console menus. Presumably the upcoming "Zelda 3DS" will also use the stylus.

Phantom Hourglass Stylus
During the beginning parts of Phantom Hourglass' release, Nintendo of America ran a promotion in which, after registering the game on their Web site and taking the subsequent survey, they would send the person a Phantom Hourglass-themed stylus which is clear-colored and shaped like a feather pen.