Capured cannons and aircraft
Unexploded ordnance (UXO)
Depends on which side you're on...Photos showing wounded and dead civilians
Statue made from pieces of shrapnel
On the grounds of the War Remnants Museum is a replica of a French Prison, complete with cells, high stone walls, bars, and the guillotine.
A captured UH-1 Huey gunship with 101st Airborne Division markings
I'm pretty sure that's not standard U.S. Army issue...
Interestingly, though, you could get Zippo-type lighters with various insignia welded to them, dog-tags, and other "authentic" items.
The wreckage of a U.S. aircraft, downed during the Vietnam War, rests today in Hanoi's Army Museum
Turkish infantry trenches, Gallipoli Battlefield, World War I, Turkey