I saw the Veteran's day thread, but lets also remember this holiday's origin as remembrance day for WW-I. In much of the world that's still the focus of the holiday.
Believe it or not, there are still about two dozen living veterans of that war. Here is a list
As for veterans of the infamous trenches on the Western front, I understand only 2 survive, one British and one French.
The British man, Harry Patch, was a veteran of the Battle of Passchendaele. He's interviewed here
He visited the trenches on the 90th anniversary of the battle. There's a story about his visit here