I would have to say based in my observations and experience that the two most popular are the Speer Gold Dot and the Winchester Ranger Bonded in whatever caliber flavor the agency/department authorizes. Remington Golden Saber and Federal Hydra Shok and HST are also still in use. I don't know if its an equal split. In 40 caliber, I mostly see bullets of the 180 grain variety, while 45s still tend to be the proven 230 grain. As 9mm is resurging in popularity, I can't say what is most common. My folks mandate the 147 grain, either Ranger Bonded or Hydra Shok for carrying 9s, and the Winchester 147 is reputed to be much better than the Hydra Shok. The 124 grain bullets seem to be gaining in popularity. The Winchester Ranger 127 grain +P+ has been around for a while, but I'm not hearing anyone complain about its lack of effectiveness; just like the old Federal 115 grain +P+ BPLE.