The Legend of Zelda: Ocarina of Time Master Quest
There is only one fundamental difference between Master Quest and the original Ocarina of Time - the dungeons. Master Quest was made and released in Japan not too long after Ocarina, and was simply what it claimed to be: a quest for masters of the game. The sole difference is that the dungeons are 'remixed' in MQ. Otherwise, it is absolutely identical to The Legend of Zelda: Ocarina of Time.
Some of Master Quest's changes aren't particularly noticeable, some may actually make the dungeons easier; but for the most part, they make things significantly more difficult. There are a number of instances where more acute observation and ingenuity is required than ever before in Ocarina, and it's impossible to get through Master Quest successfully without remembering old Ocarina tricks and exploiting them to your advantage. Admittedly, it can get frustrating, but it's also a fun challenge.
Master Quest is a classic and highly-appraised game with a few additional dashes of difficulty. Plus, if you got it in the bonus disc from preordering The Legend of Zelda: The Wind Waker, it's free. Hard to argue with that.
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