Aside from Azelf, what was the first Sinnoh Pokémon that you caught? Mine was Piplup, the adorable little penguin!
Do Fossils count? If so, then it would be one of those. If not, then nothing. I've only seen...about six new things? And none of them are really all that interesting.
It seems everyone caught Piplup first, and I'm no exception! XD After the penguin, I got Bidoof and Starly. Classic Sinnoh progression.