Looks like Nintendo is done teasing Pokéfans with new features of the upcoming DS title Pokémon Black & White. Now they're just flat-out offering incentives to get you pumped up for its release.
If you buy either of the versions of the new game between its March 6 launch and April 10, you'll be able to receive a special Liberty Pass via the Nintendo WiFi Connection which will allow you to catch the never-before-seen Mythical Pokémon Victini.
This Victory Pokémon is Psychic- and Fire-type, and can't be caught during normal gameplay. Victini is rumored to create an unlimited supply of energy that it shares with others to ensure victory. His unique Victory Star ability increases not only his own accuracy in battle, but all of his fellow Pokémon warriors. So he'll be particularly useful in Triple Battles, which as I've mentioned before, are debuting in Pokémon Black and Pokémon White.
So if you really, truly wanna catch 'em all, you'd better get an early start!