Hey Everyone!

I've been reading the boards for years now, but decided to finally contribute.
I've been playing more classic games lately and have noticed their puzzles are harder and much longer than puzzles I've done today.For example, the temples in FFX or the puzzles seen in the Resident Evil games. I wish the puzzles and riddles could be just as difficult; it always left a sense of accomplishment. So my question is:

What is your favorite Riddle or Puzzle you've played in a game and why?