Gallipoli, Hamburger Hill, Das Boot, Apocalypse Now AND Redux for sure.

How about?:

The Big Red One (1980, Sam Fuller!)
Paths of Glory (Kubrick)
The Deer Hunter
Al Quiet on the Western Front (1930 original)
Three Kings
Birdy (only partially a "war movie")
Johnny Got His Gun (ditto)

I could do without Gettysburg and Spielberg. Cold Mountain can suck my big red one, DB.