Have to give a shoutout to all the above, and also throw in a word for Fire in the Lake (GMT) and Hearts and Minds (3rd Edition with Compass)-- both are strategic-level Card-driven games that to my mind do great jobs of capturing the historical flavor of the conflict (gamey aspects notwithstanding). MMP just released Front Toward Enemy, which is a tactical-level game and the initial feedback I've seen is pretty positive (I can only comment on the physical components, which are nice).
Of the aforementioned games, Silver Bayonet, Heroes of the Nam and, in particular, Dien Bien Phu: The Final Gamble are worth searching out.
Boonierat-- re: Rumor of War, I purchased it from Compass on release and the components are lovely. I haven't taken a dive into the rules yet because Hearts and Minds arrived on my doorstep shortly afterwards and ate up my time. I'd also heard some concerns expressed about a rule system first used for a Korea game (Korea: Fire and Ice) being fitted for Vietnam as well, and whether that was feasible given the differing nature of the conflicts. That said, I've had great experiences corresponding with designer Adam Starkweather re: rules clarifications, etc on his other games-- he's courteous, prompt in replying, and very patient-- so it could be worth taking the jump if you're curious.
One final game of note: The War in Vietnam (the forum won't let me post a link but you can search for it on Kickstarter). Slated to be an Axis & Allies-style game with 800+ pieces. I'm on the Kickstarter roster and am eager to see how this one turns out.