The UH-1 Iroquois ("Huey"), developed by Bell Helicopter, was a pilot's dream, and one of the most versatile aircraft of its time, although it was not ideally suited to jungle operations in Vietnam, and had some critical design flaws that limited its overall effectiveness.
Pilots of the Huey marveled at its responsive controls, agile handling, and rugged engineering. A pilot could pick up eight or so soldiers, drop them into a battle zone, pick up wounded, take them to the hospital, then land in a shallow river to wash the decks. It could haul men, supplies, even trash. Skilled pilots could run resupply missions in the dark on the side of a sloping hill, and could land and take off in very narrow spaces. So the Huey was a workhorse of the US Army in Vietnam and in general it was loved by the men who flew them and depended on them.
However, the flight requirements of the missions they flew meant the Huey had too little armor plating, and left the pilots overexposed to ground fire through the plexiglass windows and thin steel plating on the floor. The doors were most often removed for ease of use, but this made them easy targets for snipers and rocket propelled grenades. The tail rotors were vulnerable (as with all helicopters) and the aircraft could not stay aloft without one.
As a testament, however, to its effectiveness, the Huey was only very recently retired from military service, and is still prominently used in the militaries of Mexico, El Salvador and Colombia.
For a great read on the Huey and its pilots, read Chickenhawk by Robert Mason, or CW2 by Layne Heath.