Noblegarden Egg, which allows you to lay a Brightly Colored Egg. Yes, that's five eggs for one egg of your own, which is a pretty horrible exchange rate.
What's so cool about it? They're the exact same eggs you've been picking up that whole time, except that you can set them out. You can loot them right away for an added chance of whatever loot may be in them, but I'm not sure why you'd do that, except for possibly completing Dressed for the Occasion/Sunday's Finest. What makes it better is that other people can loot them.
What makes that so great? If you can get an organized crew (and their alts) together, you can set up your own Noblegarden Hunt for your guild or your friends and family. Laying an egg has a 1 hour cooldown, so each of you will only be able to set out one egg each, but with a sizable group that might not be too terrible. A brief hunt, but you can make it exciting! Feralas, perhaps? Icecrown? The interior of a cleared Ulduar? Just take it far, far away from busy cities or hubs. You don't want to lay an egg out in the Stormwind Trade District. Joe McMullet will loot that thing in a flash, and that's no good.