There is no doubt (to my mind) that the Huey (really the H model)takes the prize. Here is what I penned this morning to send to some folks (The olive drab green text is quite intentional):
Today, October 20th 1956, the U.S. Army XH-40 prototype helicopter flew for the first time. This aircraft was the first turbine powered helicopter in the Army fleet and was powered by a 700 shaft horsepower Lycoming XT-53-L-1. The Army was not slow to accept the aircraft and it became the UH-1 Huey. The variant we now fly is a bit bigger than the XH-40 and has more than twice the available horsepower. This is the 60th anniversary of that flight. The UH-1 was also largely responsible for the initiation of the Warrant Officer flight training program which allowed high school graduates to become Army aviators without being commissioned officers. Hats off to all the aircraft still flying or those that are on sticks in parks and museums as well as to the people who maintain and fly them.
It took a twin engined machine to replace it. The Huey is up there with the DC3/C-47 and considering that at its best it isn't the smoothest flying ship in the world, it is outstanding that it just keeps going and going if you care for it.