An Epic Battle with these;
Natsu Dragneel VS Dragon Force or Lightning Flame Mode VS
Rin Okurmura (Blue Exorcist) Sword Released  VS
Portgas D Ace (One Piece)  VS
Head Captain Yamamoto (Bleach) Shikai only  VS
Tsuna Sawada (Hitman Reborn) Hyper Dying Will Mode or Ultimate Dying Will Mode 
Any Form of any character allowed (Except Yamamoto's bankai because it'll be to overpowered), An example would be Natsu's Lightning Flame Mode or Tsuna's Ultimate Dying will Mode. A Youtube video link is provided if you don't know much about the characters.
It can also be the character in any point of time, so Natsu time skip or Tsuna at the end of the Hitman Reborn Manga.
Anything goes. Who wins?
Also who do want to see for Project Versus J. The game for Shonen Jump. We already Naruto, One Piece, Bleach, Dragonball Z and Toriko are gonna make an appearance but if you had the choice who would you choose? For me it'll go a bit like this...
Tsuna and his guardians - Hitman Reborn;
(If possible) Natsu and Gray;
Gon and Killua - HunterxHunter;
Gintoki - Gintama;
Yusuke and Heie - Yu Yu Hakusho and;
Kenshin Himura - Rourin Kenshin
What would be you pick?