I heard the Y12 Swat team from Oak Ridge TN had the Number 1 Swat team for many years. Do not know if they are the current number 1 or how true this is since I heard it and not verified it.
About Y-12 Special Response Teams - The Department of Energy Y-12 Plant is located in Oak Ridge, Tennessee and is tasked with manufacturing and reworking nuclear weapon components, dismantling nuclear weapon components returned from the national arsenal, serves as the nation's storehouse for special nuclear material (SNM), and provides special production support to various programs. The Special Response Teams (SRT) are tasked with the mission to protect nuclear weapon components and special nuclear material (SNM) with deadly force if necessary. These teams are filled with professionals that have served in the Military and local, state and federal Law Enforcement. It is not uncommon to find former Marines, Rangers, Special Forces, and Air Force Security Police veterans serving in various positions within the teams. Additional, all team members go through extensive initial training and regular testing to gain and keep their position. Qualification standards include bi-annual marksmanship testing with all team weapons. Some of those qualifications include precision shooting while on the move (no easy skill), obstacle course that includes engaging various targets while negotiating obstacles, individual and team building assaults (CQB) in both day and night conditions, and various other physical and written test. In all, they receive more that ten times the annual training time of some Law Enforcement departments.
See More here.
http://www.specialoperations.com/Domestic/DOE/Y12.htm