Hamburger Hill is my favorite Vietnam Movie. We Were Soldiers is another good one. Of course Band of Brothers and Saving Private Ryan. Black Hawk Down....shit....what else...
Oh yeah, i remember an AE WW1 movie that came out that was pretty good. Called "The Lost Battalion". Check it out.
A pretty good movie based on a the true story of Soldiers from the 77th Division who were cut off and surrounded by the Germans and fought on until friendly units could break through to them.