I just saw this article on Gamespot about the new Halo, and one of it’s new modes. This seems really cool. The long and short of it is that you can edit on-line maps on the fly. Say you’ve got 4 guys running around blowing each other up, and you decide right here and now would be a good place to find a rocket launcher, you can go and drop one right there for you to pick up.
Viva la mayhem.