Anyone who owns Pokemon HeartGold or SoulSilver for the DS should bring it to Pokemon League this weekend. Starting this Saturday (July 31st), Nintendo will be distributing the Enigma Stone over WiFi. The Enigma Stone allows you to encounter Latios (in HeartGold) and Latias (in SoulSilver)! After you catch the one in your game, the Enigma Stone turns into a Soul Dew which powers up both Latios and Latias abilities in battle. Hillside Games has WiFi that you can access to receive this item.
In order to access Latios and Latias, you need to have beaten the Elite Four, gotten the National Pokedex, and have two or fewer Wonder Cards. Even if you haven't accomplished these items now, you can still get the item to use in the future. When you encounter Latios or Latias, it will be level 40.
Also, did you know you can earn League points for battling on your DS? You most certainly can. Also, you can earn cool skins for your DS the same way you can earn promos! So, there are multiple reasons for you to bring your DS to Pokemon League.