Vietnam 1965-1975 by Victory Games (1984) - The Grandaddy of them all designed by Nick Karp.
"This simulation game re-creates one of the longest, most complex, and least understood conflicts in US history in all of its military and political aspects.The rules include detailed treatment of movement, terrain, search and destroy operations, special operations, firepower, air mobility, riverine, brigade-level formations, limited intelligence and auxiliary units in each scenario. The scenarios start out small with Operation Starlite, and slowly build in complexity, introducing more rules, until the entire Campaign Scenario which covers the entire war from 1965 to 1975 and introduces South Vietnamese politics, morale and commitment, strategic bombing, reinforcements, and pacification. Unit counters are Battalion and Regiment size."
It's also getting a remake by GMT Games with updated artwork and rules revisions! Check it out over here on the games page!
Silver Bayonet: The First Team in Vietnam, 1965 (25th Anniversary Edition) (2016) - Designed by Mitchell Land and Gene Billingsley
"Silver Bayonet recreates the pivotal November 1965 battle between a full North Vietnamese Army Division and the US 1st Air Cavalry Division in the Ia Drang Valley. NVA expertise in lure and ambush tactics resulted in significant US casualties. US mobility and the ability to bring massive amounts of firepower to bear quickly virtually destroyed the attacking NVA division and forced a change in NVA tactics."
Downtown: Air War Over Hanoi, 1965-1972 - (2004) - Designed by Lee Brimmicombe-Wood
"Downtown: Air War Over Hanoi, 1965-1972 is a game of air warfare over Hanoi. During the Rolling Thunder (1965-68) and Linebacker (1972) campaigns, Hanoi and the Red River Valley was the focus of American air operations intended to pressure North Vietnam's Communist leadership into ceasing their attacks on the South. Against large "packages" of US attack and support aircraft, the Vietnamese deployed a formidable array of anti-aircraft artillery (AAA) and Surface to Air Missiles (SAMs)."