I haven't found a build I liked as much as Imperial Ar, honestly. It was the only city I've found that was actually built with good, realistic defenses in mind. That wall was enough to break most attempts at "raids" just by virtue of existing, and once you tossed a few ballista up top? Yeah, no contest.
Given my enjoyment of combat, I like any build that turns attacking a city into the painful, difficult experience it's supposed to be.