Usually, people run Outrage, however, if you really want to, use Draco Meteor. Since when you KO a mon with Regidrago, they would probably bring in a counter, and since you used Draco Meteor, you're getting out of there. HOWEVER. I strongly advise that you go physical. Physical is like a million times better because of Dragon Dance. However, if you really want to use special, run Draco Meteor as it's probably not going to outspeed, and big damage will probably be dealt to it as it has horrible bulk (other than hp)