JEWELCRAFTING:
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[Vicious Amberjewel Band] - DEs into
[Heavenly Shard] and the mats are generally plentiful/cheap on the AH.
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[Sapphire Pendant of Winter Night] - Even though the craft on this item takes 15 seconds it's probably my favorite JC item to DE. Usually DEs into 1 or 2
[Illusion Dust], but sometimes you'll get 1 or 2
[Greater Eternal Essence] or even a
[Large Brilliant Shard]. Just keep an eye on
[Essence of Undeath] and
[Blue Sapphire] and buy them when they're cheap. I frequently make these for as little as 4-6g investment.
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[Onslaught Ring],
[Glowing Thorium Band],
[Emerald Lion Ring] - Same story as the one above, but these tend to be a little more expensive to craft. Still just as amazing when you can get ahold of the materials cheap.
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[Band of Natural Fire] - This one almost didnt make my list simply because it has been my experience that it's hard to get ahold of bulk
[Living Essence] for a decent cost. Regardless this item DEs into
[Large Brilliant Shard] which makes it a very valuable craft if you can get ahold of the mats.
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[Bloodstone Band],
[Crystal Chalcedony Amulet],
[Crystal Citrine Necklace],
[Sun Rock Ring] - Alot of people know about these from doing the Saronite Ore shuffle back in the day and that shuffle is still viable to this day.
[Infinite Dust] has and will continue to have a very high demand due to its importance in leveling Enchanting and being able to craft your own source of this Dust is a good thing.
Honorable Mentions
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[Nightstone Choker] and
[Hessonite Band] - Both of these items when crafted have a higher chance of Disenchanting into
[Lesser Celestial Essence] than the ones crafted with Jaspers or Alicites. What also makes crafting them even better is that when you proc a blue craft on these they DE into a full
[Heavenly Shard] unlike the items created by Jaspers and Alicites. I only recommend doing these if you are already shuffling ore.
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[Carnelian Spikes](Idea courtesy of @zenga ) - This one can DE into as many as 3
[Greater Celestial Essence](before Bountiful Bags), but does also sometimes yield Hypnotic Dust. On average you end up getting about 2 GCE per DE so you have to calculate the cost of 3 Carnelian plus 3 settings and decide if this DE is worth it for you.
BLACKSMITHING:
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[Stormforged Shoulders] - This item is my main source of
[Heavenly Shard] as it is easy to get a hold of the materials in bulk. Your main investment in making these will be time if you Smelt the bars for it yourself(which I definitely recommend). A great way to keep your Enchanting costs low and your Scroll profits high!
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[Enchanted Thorium Blades] - This is an amazing item to DE. It is how I keep myself well stocked on
[Greater Eternal Essence]. This can also DE into
[Illusion Dust] or on rare occasions a
[Large Brilliant Shard], but 75% of the time you get good ol' GEEs a-plenty. Do this one while you can as Blizzard is removing the ranged/relic slot in MoP and therefore any recipes which create items for that slot go bye-bye too.
TAILORING:
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[Wizardweave Turban] - This item is probably my favorite item to disenchant in the game. Out of all the craftable items that DE into
[Illusion Dust] and/or
[Greater Eternal Essence] this one just gives more of them per DE on average. I've gotten as many as 8 GEE from one DE(granted Bountiful Bags was involved). Mostly these just DE into a ton of Dust but they give Essences pretty frequently as well. Mainly keep an eye out for cheap
[Star Ruby] and it shouldn't be hard to find the rest of the materials in bulk cheap.
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(Idea courtesy of @Finkz) - This one is not learned by the Tailoring trainer but is rather a rare drop recipe from Vanilla mobs. Really cheap to make for decent returns if done in bulk. Keep an eye out on the AH for the pattern.
Honorable Mention
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[Runecloth Headband] - Doesn't require any Dust or Rubies like the Wizardweave Turban so it's a decent fallback item to DE in the Turban's place when you can't get the other mats cheap.