FBI uses: Winchester PDX1 (civilian marketing) which is the Winchester Ranger Bonded
BSO (Broward Sheriff's Department in FL): AFAIK uses Winchester Ranger (i.e RA40T) in various calibers
NYPD: Speer Gold Dot

There's a lot of agencies out in CA that have switched to Federal HST.

That's just a small list of what I know, but things change year to year as budgets tighten.