Hawkeye

The Hawkeye is an item in Twilight Princess which lets you see very far away objects. It is similar to the Telescope in The Wind Waker. You can combine it with the Hero's Bow to be used as a sort of sniper scope. The Hawkeye is a one of a kind item that can only be purchased at the Kakariko Village Malo Mart after completing the bow minigame. It is an optional object. You find it after talking to Talo in the top of Kakariko Village and finish the mini game.

Image taken from Zelda Elements