This is going to be my submission to Gameflood's contest this year.
It's a building on the coast that's being attacked by ships, but the area is frozen in time, and the building is in the middle of collapsing.
The arena is the inside of that small building, with holes in it large enough to see outside, and enough debris in the air to block half of what they throw at you. Plus all of those weird angles make for some interesting ar2 fights.
Check it out and give me ideas and bug reports in the forum topic.