Double Clawshots
While Twilight Princess features a variation of the Hookshot, once reaching the seventh dungeon (City in the Sky) you'll receive the Double Clawshot. This item works very similarly to Spider-Man's web technique, enabling Link to grapple onto an object while holding onto (or swinging from) another. This is required to go deeper into the dungeon.
The visible difference is that previously, when Link grappled onto a target, his only option was to drop to the platform below. However, the combination of two clawshots allows his to grapple and pull himself towards one target, then grapple another target without the need to drop down before hand. This is vital, since many sections of the City in the Sky have pitfalls and holes instead of solid platforms.
The Double Clawshot is the key item to defeating the boss of the city in the sky, Argorok.