I am also routing for Ace, Roy, Takuya, Hiei or Zancrow to win.

I was going for Roy due to his experience, but Natsu can eat fire. Doesn't that basically ruin everyone's chances of winning as long as they use fire? All of them use fire, so therefore...

The Head Captain of the Gotei 13 from Bleach. His Zanpukuto is the most powerful in Bleach and he has other methods of fighting, also, being a Master of Kido, hand to hand combat and a Master swordsmen. I apologise for not posting a picture, but, being on my cellphone, I cannot. I know for sure that he would absolutely destroy Natsu, Ace and Tsuna. As I don't know much about the others, I can't answer for them.

@Fandomfan. Old Man Yama has a thousand years of pure fighting experience and would work out a way to defeat Natsu. He can create huge amounts of fire and spirit energy, plus Natsu has a limit to how much fire he can ingest.

If it were to really happen, I would like for either Roy, or Kyoko-chan to win. :)
..and I do think that Roy is the strongest, overall (from the ones I know).

2.Roy
3. Tsuna

Natsu and Tsunayoshi <3

rin okumura and maybe natsu