Well, the hardest Temple for me was the Lakebed Temple. It was really hard for me since it was my first Zelda game and it took me a week to beat. Even today when I play it I always forget to get the boss key.
I found the Lakebed temple one of the hardest temples (Mostly in twilight princess,) because it took a while for me to figure out how to get in the temple, and then getting to different rooms by making the stairs rotate, and going from room to room turning on the water and fighting monsters. Finding the boss key was difficult, and then there was those clams and electric jelly fish, fighting the boss was not that hard but it still took awhile. I only beat that temple with the help of Zelda dungeons.net
The hardest dungeon I thought was in the Zelda games was the Cave of Ordeals just because of all the enemies and challenges leading up to the fairies. Also, I thought the three black knights ganging up on Link in one of the dungeons in the cave was very difficult to maneuver around, but in my mind, this area takes skill, items, and the power of the Twilight wolf!
Congrats to all the winners. Just forewarning everybody and not just the winners. I will be announcing our next giveaway contest in the coming days. However, this one will span the entirety of the month of January and will have a bigger grand prize. Furthermore, it will require a higher post count so let's keep those posts flowing!