From now until April 8, anyone in Europe, North America, or Australia with a copy of Pokemon Black or White can download a Reshiram (Pokemon White) or Zekrom (Pokemon Black) from Nintendo WiFi. These Pokemon are at Level 100, carry a Dragon Gem (which grants a one-time boost of a Dragon-type attack), and have the exclusive moves Mist (Reshiram) or Haze (Zekrom). These special Pokemon also unlock a special area in the Dream World where you can play a mini-game to unlock a very special C-Gear skin.
Also, you can get a Victini doll to decorate your Dream World home. The password is: PGLVICTNI12.