Patton
The Dirty Dozen
Hannibal Brooks
Ice Cold in Alex
The Train
The Searchers
Butch Cassidy and the Sundance Kid
The Wild Bunch
Tombstone
12 Angry Men
The Sting (a bit newer, but great)
edit, sorry I didn't see the 'war and westerns' requirement!
To the OP, I second Bledd's recommendation for '12 Angry Men (1957)' - excellent film.
I would think ' High Noon (1952)' would be first on my list for classic westerns. Probably, also in top ten of my favourites.