For me it was the Water Temple from Ocarina of Time lol. It had puzzles that spanned from the top to the bottom of the temple, not mentioning the enemies you had to face to get those objectives completed. I figured out most of the secrets of the middle pillar by the time I got to the untouchable heart piece. No matter how hard I tried It would never come within my reach. Making the water level rise was no easy task when you had to combine the right water risers to complete your task. I would play for one when I Really needed to play for the next. I had a hard time when it came to fight Dark Link. I tried to beat him with the Zelda Dungeon guide, but my Dark Link must have been specially programed because it would block every sword thrust and backflip when I used the hammer. I finally beat it when I used the hookshot, which is pretty ironic considering it was guarding the longshot.
I originally thought it would be easier with the longshot, but I was wrong. It only got more complexing puzzles to defeat. I thought that going up to morpha's lair would easy knowing how to avoid the spike traps, you can guess what I'm gonna say now. I lost half my hearts getting up when I discovered that I did not have the boss key. The vortex maze was hazardous and deadly especially when tektites are trying to knock you in. I was confused when I got to the end of the terrible river, there was nothing left but a door that would only lead me to go in circles until i noticed the hole in the ground that the boulders would not sink into. When at last I got to Morpha I had to try three times to kill it. Morpha is a fairly easy boss, The reason for my three failures is the way in which I tried to kill Morpha.
When I had finished the water temple I was free to continue to the Shadow temple and my favorite temple. Hope that this was Enough to satisfy the judge, and may the best zelda lover win!