Powders.

Everyone knows what Oriharukon and Laktoreruim means, anyway so I get 5,000 BCoins more out of my "salary", let's talk about them in deep.
Powders are used for many, many, many, many, many, many, many things. Refining capes, weapons and armor, upgrading Celestial God's capes, unlocking level limits and a wide variety of items that are too many to mention right now (so I'll just list them in a sec). OK, so there are two types of Powders, as I said before, Oriharukon and Laktorerium:
-Oriharukon: The orange one.
-Refines: All kinds of armor and weapons, fairies, accessories and capes (except Celestial God's cape) up to +6.
-Upgrades: Firals to Enamels (the color stuff), Ores to God Stones (the ones used to make Sephirot, kinda look like an orange oval)
-Combined For: The following Jewels (made with Hunter Class' Jewel Craft Skill): Life Steal Jewel and Shield Jewel.
-Obtainable Through: Monster drop, event, other players, talking to NPC Jeffy in Azran sacrificing 10 Oriharukon Scraps and 1 million Gold in your inventory or talking to NPC Ehre in Erion sacrificing any +9 item and two Sapphires in your inventory.
-Latorerium: The purple one.
-Refines: All kinds of armor and weapons, fairies, accessories and capes (except Celestial God's cape) up to +9 and armor and weapons from +10 to +11. Accessories (Earrings in this case) can be refined up to +11 with Laktorerium, though if you fail +10 or +11 the item disappears.
-Upgrades: Firals to Enamels (the color stuff), Ores to God Stones.
-Combined For: Mount Growth Stabilizer, refining Celestial God's cape, unlocking Level 350 and 370 God's Experience Limit, the following Jewels (made with Hunter Class' Jewel Craft Skill): Elemental Jewel and wise Jewel.
-Obtainable Through: Monster drop, event, other players or talking to NPC Jeffy in Azran sacrificing 10 Oriharukon Scraps and 1 million Gold in your inventory.
I might forget about some other uses, but feel free to ask any player about them. Most of the people will help if it doesn't have to do with giving money or items away (really-direct-indirect for those pesky beggars).

In-game avatar for Powders:

-Trivia:
-Get as many Scraps as you can, as Jeffy only charges 1 million Gold for each time you combine the items. That mean that making 10 Oriharukon Powders with 100 Oriharukon Scraps costs the same (1 million Gold) as making only one with 10 Oriharukon Scraps.
-If no one's buying your Oriharukon Powders don't hesitate to sell them to any NPC (in a relatively low Tax-Rate Server, like 5%). You can sell them for 800,000 Gold, while you can sell them for 1,000,000 Gold to any player. It's a 200,000 Gold loss, but if you're in a hurry... --- "Prices may vary at the time you read this. As for now (February, 21st, 2012) Oriharukon Powders cost around 1 million Gold if you buy them from another player and 800,000 Gold when you sell it to any NPC."
-NEVER, EVER USE LAKTORERIUM POWDERS TO UPGRADE STUFF TO +6. Oriharukon is really, really cheaper and does the same job.
-PK any character who sells Laktorerium Powders overpriced when you have the chance. Maybe they'll learn.

OK guys, stay tuned for more useless stuff that you already know... Nah, "just kidding"... Yeah, right...