With the AI doing interesting things in Halo 3, I'm extremely interested in the new Brutes, their tactics, how they handle combat individually and the physical manifestation of the "Brute Pack" concept. I've talked about this with Ghaleon before, but it's going to be interesting to see how they introduce equipment into combat. Will it be completely scripted, will there be some AI integrated into it, telling the enemies to make good judgment when using them in combat. It opens up a whole new approach to what you should expect from an enemy in a video game.
In Halo 1 and 2, if you have an elevated position, they can shoot at you, toss nades up and maybe even try to flank you, but what if one of them has the portable gravity lift. Now you've got that to deal with as well...