My favorite war movie has to be Patton. I could watch it over and over.
If you have ever seen Pork Chop Hill with Gregory Peck (not to be confused with Hamburger Hill) it's good too.
My favorite war film of all time is Apocalypse Now, written largely by NRA board member John Milius, btw.
See the restored version of "The Big Red One", one of the best war movies ever.