In the meantime I was discussing the question with bacon and we found a small loophole. Don't worry, this doesn't change anybody's guesses. For the sake of this question, the Outrage cannot land a critical hit.
Um...didn't DNA say no items? So Arceus doesn't even get STAB from it. Plus, he only has 120 base attack, Rayquaza, Zekrom and Giratina-O all have 150 iirc.
Gyarados is incorrect. Dark Void is right - Arceus wouldn't get STAB off it at all, and even so it's got 120 base compared to the 150 base people have kept saying. And Dark Void hasn't used up his guess yet. lolfail
@Catutie: Right, because you are totally allowed to use held items in this question.
@Azelf Master: I'm going to keep it secret until someone actually answers, but if you want, you're free to PM me with your guess. Just no points will be gotten from it.