Halo: Reach, you might want to flip to one of the many other stories we've written about the game. If you want super esoteric insight into the high-functioning AI design of the series -- that is to say, the enemies' actual programmed intelligence, and not the game's fictional AI constructs -- we suggest checking out AI Game Dev's 42-point analysis on Bungie's tricks and innovations for making those pesky Elites so darn pesky.
Of course, these tips will really only benefit you if you happen to be a game designer or programmer, though we suppose you could hypothetically use the information to impress your friends while playing Reach next week. "Look at the way Bungie implemented those perceptual information objects," you might say to your awestruck cohorts. "Man, that really must have cut down on some memory fragmentation and recycling problems."