My full-time department issues the following:
Beretta 96FS with Trijicon Night Sights
Benelli Nova 12 gauge
Ruger Mini-14 stainless Ranch Rifle w/ 20 round mags
Patrol/uniform officers are required to carry the Beretta and have the long guns available in the cruiser.
Our plain clothes officers/detectives have the option of carrying a department issued SIG-Sauer P229 or Beretta 84 instead of the Beretta 96. They are also authorized to carry personal weapons on-duty so long as they are approved by the chief and qualified with. I'd like to see that extended to everyone, but I don't really see that happening. We are not a large department, we are at about 40 sworn right now.
Off-duty and backup guns are pretty much up to us. They just have to be qualified with and approved by the chief. At the moment I carry a S&W 37-2 as a backup and a HK P2000 LEM 9mm off-duty.
My part-time department doesn't issue weapons at all, other than PD issued OC spray. We are required to provide our own duty gear, batons if we want them, and firearms. Pretty much any quality weapon that we can qualify with is OK with the chief. Since I'm a gun nut, I have several, my two duty weapons are:
-S&W M&P45 with Trijicons
-Beretta M9A1 with Trijicons
I carry one or the other, depending on my mood, I have a complete duty rig for both weapons using the same holster and locations for equipment. I also qualified with my Beretta CX4 Storm 9mm since it uses the same magazines as my M9A1. Hopefully I'll get around to purchasing a 5.56mm rifle before qualification rolls around next year. For off-duty and backup I use the same guns that I do at my full-time department.
I hope to be a chief one day. When that day comes I plan to issue one 9mm pistol to everyone. Officers will be allowed to carry personally owned weapons from a vast approved list, but that will require them to provide their own holsters, weapons, and ammunition if the duty weapon they choose is not a 9mm. I hope this will mean that only the shooters will select to carry a personal weapon and the non-shooters will all have the same weapon making it easier for my instructors to teach those who need it.