Berets of the United States Army
U.S. Army Special Forces wear the green beret because of their link to the British Commandos of World War II. The first Ranger unit, commonly known as Darby's Rangers, was formed in Northern Ireland during the summer of 1942. On completion of training at the Commando Training Depot at Achnacarry Castle in Scotland, those Rangers had the right to wear the British Commando green beret, but it was not part of the regulation uniform at the time and was disallowed by the U.S. Army. 
The 10th Special Forces Group (Airborne) had many veterans of World War II and Korea in its ranks when it was formed in 1952. Members of the 10th SFG began to unofficially wear a variety of berets while training, some favoring the red or maroon airborne beret, the black beret, or the green commando beret. In 1953, a beret whose design was based on that of the Canadian Army pattern, and which was rifle-green in color, was chosen for wear by Special Forces units.
Sam Browne belt
The Sam Browne belt is largely obsolete in police and security use due to risk of strangulation by potential opponents. It has sometimes been referred to as a "Suicide Belt" by personnel. It had enjoyed some popularity with civilian police agencies worldwide and was probably most widely worn in this context during the 1940s and 1950s. This use has gradually faded out due to field safety concerns. It is part of the ceremonial dress uniform of many agencies, most notably the Red Serge worn by the Royal Canadian Mounted Police. The RCMP enlisted ranks wear the cross belt over the left shoulder to support the pistol worn on the right side. RCMP commissioned officers wear the cross strap over the right shoulder due to the need to support a sword when wearing the red serge ceremonial uniform. This difference of wearing the cross strap over different shoulders for commissioned and non-commissioned members is even maintained when wearing the stripped Sam Browne belt (no pistol or sword).
The Sam Browne belt has been proposed as a solution to occupational safety and health concerns about injury due to the weight of equipment on police officers' belts. However, others have expressed concern that the vertical design of the belt could enable criminals to gain physical control of law enforcement officers in an altercation.