The Sig P320 (M17/M18) is the successor to the Beretta 92 (M9) as the US military's standard service pistol.

Glocks are the most common among law enforcement in the US these days. The FBI's service pistol is a Glock 19M. Glock claims that the Glock 22 is, "by far the most popular police service pistol in the United States," which surprises me because the 17 and 19 are the service handguns at most big cities, AFAIK.