Essence of Competition

During the Beijing 2008 Summer Olympics by winning any battleground on any level you had a chance to receive a Gold Medallion via the in-game mail. The Gold Medallion in fact summons (spell) a mini-pet called the Spirit of Competition (picture) in the form of a Chinese dragon.

By participating in a battleground game on any battleground, on any level, you would, during that time, always receive a Competitor's Tabard, whether you won or lost.

You can find more information about the Spirit of Competition event (deprecated url) on the European World of Warcraft info pages.

Talking to a commoner during the Olympics in any of the capital cities gave you further information on how to gain these items.

Every two years the Spirits of Competition grow especially fervent... and now is that time! We wear this tabard into the Battlegrounds to honor them, seeking to defeat our enemies and earn their favor.

Q: How do I earn a Competitor's Tabard?
A: You need only face our rivals in any of the Battlegrounds. Win or lose, if you stay for the duration of the battle, you will be mailed a Competitor's Tabard.

Q: How can I gain the favor of a Spirit of Competition?
A: You must defeat our rivals in any of the Battlegrounds. With every victory, there is a chance that a Gold Medallion will be mailed to you.

You got an in-game mail when you received one of these prizes.

Competitor's Tabard
You fought bravely in a battleground and impressed the Spirits of Competition... Well done! As a reward, you have been gifted with this mark of favor; a Competitor's Tabard. Wear it proudly.

Gold Medallion
You have honored the Spirits of Competition with your fervor in the face of the enemy. Congratulations! With this Gold Medallion, they will be proud to be seen at your side.

There is also a different version of the dragon mini-pet, called the Essence of Competition. You can summon (spell) it by using an item called the Competitor's Souvenir, which you were able to get by talking to the Battleground Enthusiast in either Ironforge or Orgrimmar, and giving her a secret code.

The Battleground Enthusiast in Ironforge was a female dwarf called Gilbarta Grandhammer, and she was located in the Hall of Arms in the Military Ward. The Battleground Enthusiast in Orgrimmar was a female orc called Muja, and she was located in the Hall of the Brave in the Valley of Honor.

You know the Spirits of Competition, yes?

Every two years they draw close to the mortal realm. During such times, members of both the Alliance and Horde wear Competitor's Tabards into the Battlegrounds to honor the spirits, seeking to defeat one another and earn their favor.

I stockpile souvenirs from such turbulent times. If you've learned the proper word, I might be convinced to part with one...

• I would like to enter the secret code to receive my Competitor's Souvenir.

While the Essence of Competition could be found next to the Battleground Enthusiasts, it was never released in Europe or the US as a mini-pet for players. (source)

This pet will not be released on US and EU servers. The NPCs found on those servers to redeem the code are a bug.

Throughout each day of the event in China, the code is mailed to 500 random players. Only players who have achieved various in-game milestones during the event are eligible for a chance to receive the code. Some milestones include having an Arena rating of 1650+, increasing reputation for certain Outland factions from less than revered to exalted, or raising a crafting profession from 350 or less to 375.

Hints:

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• Any battleground which you participate in, whether won or lost, will award you with the tabard.
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• Any battleground which you won may award you with the gold medallion.
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• You don't need to win 3 (or more) games in a row to get the gold medallion.
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• You don't need to be #1 in kills or healing etc. to get the gold medallion.
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• You don't need to be wearing the tabard to get the gold medallion.
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• The mini-pet seems to be of the same level as the player who acquired it.
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NOTE: THIS PET HAS NOT YET BEEN RELEASED ON EU AND US SERVERS. No official announcements have been made yet regarding how it will be obtained on those servers. In China, the pet has already been released. Throughout each day of the event, the code is mailed to 500 players who have achieved various in-game milestones, such as having an Arena rating of at least 1750. Obtaining this pet is likely to be handled differently on US and EU servers. However, there is a chance this pet will not be released in the US or EU at all. Blizzard should be releasing details in the coming week.

This is not the same as the dragon you get from the BGs, it is a completely different blue dragon.

Information about the second version of the Dragon Pet, from warcraftpets.com:

The Essence of Competition, an azure Chinese Dragon, has not yet been released on EU and US servers (trust me—this info is correct). Members who claim to have are either confusing it with the Spirit of Competition, or are they are on servers in China. In China, the pet has been released. Click the link above for details. If you have CONFIRMED information regarding this pet's item, icon, or how it's obtained, I encourage you to contact me. No rumors, please!

This Olympic event will continue for the duration of the summertime Olympic Games: August 8th through the 25th. Let your competitive spirit soar to redeem these awesome new serpents!

I could've sworn I saw the blue one in a BG last night (I'm on a US server), but maybe I was mistaken. If I had known then how rare they were I would've spammed him with tells until he told me where he got it from =)