Any kind of fighters are allowed Weiss :) If I had to be technical, I suppose something around the low-end of mid tier type of power. There´s a 10-tier system hanging around the web somewhere, but I couldn´t locate it. I´m sure someone has access to it. The way these kind of things normally work, you create a character with strengths and weaknesses, and then challenge someone to fight you with one of their characters. It is often best to agree beforehand on the powerlevel, as it wouldn´t be very interesting to have a normal person who barely knows how to fight get curbstomped by someone who can punch the moon out of orbit.
On this kind of thing, I was thinking a powerlevel around a level of over-the-top combat. Tier 4 would be such, if memory serves me right; which loosely involves being able to smash eachother through walls, carry huge weapons with ease, jump several stories up/down without any trouble, and so on and so on. For reference, think a slightly toned down Advent children type of thing.
Weiss; As for how rp combat works, if you´re new to it: http://www.roleplaygateway.com/type-turn-based-combat-eden-era-t4212.html
All in all, this fight will be more focused on blowing off steam and having an awesome looking fight, than having a super focus on "WHO DAH BEST!?"
So, I´ll ask again; Any takers?