The company I am working for has a contact to Uncle Sam. If you don't have your own gun they issue you a Ruger P89 or P95 in 9mm. I started carrying a S&W 4566 and just switched over to a S&W 4563TSW. When I first started on the job I wanted to use my S&W 681 but didn't have the duty gear for it. I shoot better with a revolver! We have all kinds of different guns being used. One guy has a Ruger Security Six in .357 mag and as far as I know he is the only one in the company using a revolver. He did buy a SR9 last year, but doesn't work armed very much any more. Colt 1911 Officers Model, S&W 915, Sigma, 5906, 4006, Glock 19 & 23, Browning High Power in .40S&W, Sig P220 & a Sig Pro are the ones I have seen.
When I worked for the Sheriff's Department a number of years ago every one had personally owned autos but one Captain. He still carried his Department issued S&W Model 66 with 2 1/2 inch barrel. In 2001 he was forced to use the newly issued Sig P226 in 9mm.