Here are two which have not yet been mentioned but they come to my mind:
"Wild Geese" Made about 1979 I believe. Richard Burton, Richard Harris and Roger Moore. One of the best African mercenary movies with lots of action with FALs, Uzi's, MAGs, Vickers, etc. It is hard to find and out of print but well worth a watch. Some of the action is a little over the top...the Uzi's bark louder than the FALs and hand grenades toss guys 20 feet in the air but it is still a good flick.
"Tom Horn" with Steve McQueen. The Winchester model 1876 should have been billed as one of the stars.
Oh, I was supposed to name 10 so here are 8 more, in no order:
Shane
Band of Brothers
Wild Bunch
Apocalypse Now
Son of the Morning Star
Tombstone
Thief
Schindler's List
There are many more I can think of but that's good for now.