Is there any field in which applicants to PhD programs (in any part of the world) usually have publications? We get occasional questions here from people who are applying to PhD programs, and are worried because they have no publications. This is puzzling to me, because most of my friends in PhD programs did not have any publications when they applied. 

We've also previous agreed that it is not generally mandatory to have a publication when applying to PhD, although it certainly helps. I am interested in knowing if there are any fields that are exceptions to this rule.

Are there any fields of study where (in some parts of the world, at least) most students have publications already by the time they apply for PhD admissions? 

By "most," I mean that publications are common enough that a lack of one is seen as worrying, and possibly indicative of some deficiency in the applicant.
I'll point toward the Max Planck School for Computer Science,
IMPRS-CS, if I remember correctly they used to have even stronger wording than the current 


  A successful candidate must...  have performed research and published (or submitted for publication) the results


But the MPIs are not the norm. Mostly, you would be fine with just your Masters thesis in math, comp sci, biology, or chemistry.