Even though I voted for Bow/Arrow, I still have some other favorite ones like: Ocarina, Longshot, Magic Rod, Hammer, Boomerang, Bombs, and Double Clawshots. Those are my other choices of favorite items.
Bow and arrow, definitely. Anything explosive is already great, and bomb arrows are just joy in projectile form. Close second with me are bombs, obviously.
The Wind Waker. It can control the wind, create cyclones, change night to day and vice versa, and allow you to take control of certain objects and people.
I voted for "Other", because my favorite item is the Light Arrow. Light Arrows from the Wind Waker specifically. Light arrows seemed very cool to me, in appearance and in concept. It's all shiny and BA looking if you press L and turn the camera around to look at Link from an angle, and it destroys pretty much any enemy in one hit. And this is also a big reason I want magic in Zelda games: the Light Arrow!
I voted for Other, my favorite item is the magnetic Gloves that appear in Oracle of Seasons, i found it entertaining and educational. it allowed you to bring yourself towards a magnet across the room or away from it. It made the puzzles more challenging by having to switch to the opposite pole in each situation. I really loved this item and it had multiple uses.
I voted for the whip, because it looks like such a fun to use items, in all that we've seen about Skyward Sword. If I had another pick, it would be bombs, because it feels good to blow stuff up!