Well, I am pretty much at the end of Legend of Zelda: Phantom Hourglass, so I guess I will write about one of the most important elements of any Legend of Zelda game: the various tools you use to do stuff. These are the treasures you get in dungeons that let you find more treasure, and thus play a central role in both gameplay and the reward mechanics. However, not all treasures are equal, and there are a too many to describe all of them in a single blog post, so I will just list some of my favorites and least favorites, in no particular order.
1) The Boomerang (original and Phantom Hourglass versions)
This item has been in pretty much every Legend of Zelda game, as part of the omnipresent Bomb, Bow, and Boomerang trinity. However, in most of them it is completely useless outside of a limited number of situations. It tends to be limited by its role as a stunning weapon, which is of minimal effectiveness in many Zelda games (only being essential in the difficult battles of the NES games), and by the fact that other weapons tend to kill or stun more easily than the boomerang does. However, the ability to guide this weapon's trajectory in Phantom Hourglass, not to mention its quiet impact sound, makes it a useful tool throughout the game, for both puzzles and battle against multiple opponents or opponents you need to hit around corners or from behind, so it never gets replaced by the more lethal Bow.
2) Bombs (Twilight Princess and Phantom Hourglass)
If any Legend of Zelda tool was perfected on its initial introduction, it is would be the Bomb. It is simple and effective, is essential in puzzles, and can be useful in combat throughout the game. The way Twilight Princess lets you choose special types of bomb for each Bomb Bag is a nice addition to the classic tool, and Phantom Hourglass is the first game where using a bomb as a weapon is very easy (a side effect of making it very easy to hit anything with a thrown object). This is pretty much the benchmark for a good Legend of Zelda item.
3) The Grappling Hook (Phantom Hourglass)
The Hookshot and its many variants have been in many games, but they are outclassed by this new item. Beyond the simple gimmick of pulling Link towards something, the Grappling Hook can also be used to create bridges, launch Link like a slingshot, and pull two connected objects towards each other. What is more, it does not rely on just set targets, but can be used in combination with mundane objects like rocks, stone tablets, and torches. Like the best of the hookshots, it doesn't just open up obvious paths, it makes you look at the terrain in a completely different way.
4) The Ocarina of Wind (Link to the Past and Minish Cap)
Yes, the Ocarina of Wind, not the Ocarina of Time. Teleportation between different places in the game is not important for puzzles or battle, but it is important for avoiding tedium. Of all the methods of teleportation in the series, this one is my favorite simply because it is quick and easy to use.
5) Empty Bottles
The simple usefulness of just being able to carry various liquids (such as healing potions!) and small items, and especially various odd things that are just floating around or laying on the ground, makes these simple glass containers a great item. I guess I should have said Bomb, Bow, Boomerang, and Bottle earlier.
6) Wolf Senses (Twilight Princess)
The various "truth" items that reveal hidden things are all god items, but the Wolf Senses manage to surpass them by just being much more cool and fun, and by letting you follow scent trails.
1) The Bow
Amazingly, the bow is not on my list of favorite items, despite being essential to every Legend of Zelda game. I guess the problem with the bow is that it tends to either be difficult to use and underpowered (in the 2D games) or overpowered to the point of pushing aside other items (in the 3D games). The Bow also tends to have a less consistent niche in puzzle-solving (other than the relatively boring role of target shooting) and no outstanding examples from any game. I want to rate it highly, but I don't think I can.
2) Ice and Fire Rods/Arrows
I do like these special arrows, and they are useful, but their combat role overlaps with the role of the Bow (direct liner attack) far too much, and few games actually use these two items to their full potential in puzzles. The Ice Arrow/Rod in particular has had a history of poor showings, and few good puzzles, despite having a solid concept. I guess they just need a slight re-imagining like the Boomerang received.
1) Roc's Cape, Zora's Flippers, and Power Bracelets
In the end, these two items just enable Link to do things he should be able to do normally and is able to do freely in other games. I am glad these have been appearing less and less as the series progresses, though they still turn up.
2) Iron Boots (Ocarina of Time)
Twilight Princess showed that these boots can be fun in some situations, but in the end they are wildly implausible and any situation in which they make sense would be better served by another item (like proper swimming gear or some other way of anchoring to the ground).
3) The Spinner and the Rod of Domination (Twilight Princess)
These two items are very fun and useful, but are completely useless outside of the dungeon they are found in. What few places they are useful are few in number and blatantly obvious. I think they are just poorly thought out items for a Legend of Zelda game. Both would be better off as unusual terrain features of particular dungeons, rather than as items.
4) The Clawshot and some Hookshots
While I praised the Hookshot and its variants above, there is a darker side to those items, Namely, any variant in which you can only target very specific and obvious targets. One of the greatest strengths of the good versions is their ability to open up routes for creative players, but these versions don't have that potential for creative use of terrain, and become boring as a result.
I think that is it for now... I might talk some more about the other items that I did not list here at a later date.