(Sorry for posting these matches a few hours early, but I won't be home tonight to do the swap at midnight. But I don't feel the results would've changed at this point.)
Pikachu & Volcanion Advance!!! I have to go with Mega Lopunny & Meloetta here. Lopunny is just incredible now, and Meloetta was so cute in the anime with all the boy Pokemon falling for it. ;)