Super Mana Potion

2400 mana on average, 33% better than the average 1800 from pre-TBC Major Mana Potions. If you use one everytime the 2-min cooldown is up, this amounts to 100 mana/5 vs. 75 mana/5.

Patch 2.1 made the mats for this potion very easy to obtain, so it's not only one of the best mana potions in the game now, but also one of the cheapest. There are still some alternatives to consider though:

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• Major Dreamless Sleep Potion, slightly more expensive mats, but gives 50% more mana, guaranteed with no randomness. And it heals hp too. But it has a drawback...
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• Fel Mana Potion, also slightly more expensive, giving a bit more mana, but with its own drawback. (The drawback does almost nothing to hunters though, so for them the only disadvantage is more expensive mats.)
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Patch 2.1 also introduced some alternate forms of Super Mana potions, related to instances. They aren't a complete substitute for making Super Mana out of alchemy mats, but they can supplement your supply and help cut down on the herb farming: Auchenai Mana Potion, Blue Ogre Brew, Cenarion Mana Salve, Bottled Nethergon Energy

Patch 2.1: "Super Mana Potions now require 2 Dreaming Glory instead of 2 Netherbloom to create."

With the Buff from http://www.wowhead.com/?item=13503 the range of restoration of this potion is increased to 2520-4200 mana.