Well, dips seem to be the consensus.

No doubt a great exercise.
I actually did have a period where my workouts were pretty much just dips, biceps curls and a lot of lower body exercises.
I will say this in opposition to dips. I have a much more noticeable upper body taper when I'm doing a lot of pull /chin ups. There's a few physique/classic guys that train at my gym and a couple of them do bodyweight bar exercises almost every workout. And their lats are borderline ridiculous for their bodytypes.
So, as great as dips are, if I was thinking about building the widest back possible, along with maximizing as much other stuff as possible, I would probably stick with chins/pulls.