I wouldn't think we include one-way couplets, but if we do, basically the entire city of Pontiac, MI is within the center of the giant roundabout which is the end of M-1 (formerly known as "Widetrack")
I've always thought that turning a freeway beltway, especially the tighter ones, into basically a freeway roundabout, would be awesome, and so good for traffic flow. I usually think about Portland, OR when I think of this idea, but a few other places, like downtown KCMO, would be perfect candidates for such a change.