A few in no particular order.
Stalingrad - After getting arrested and assigned to prisoner squads (?) The main characters lay in wait for the Russian tanks and infantry. Also when GG gets killed
That film allways gets me, I keep watching it hoping that maybe this time they'll have some luck
Saving Private Ryan - Assaulting the machine gun emplacements around the ruined outpost, nasty stuff that.
633 Squadron - The test flights in Scotland.
Memphis Belle - When the bombadier resists dropping early and takes another pass.
Platoon - When the soldiers are terrorising and then burning the village. This was a real moment for me as I first watched it, aged about 14, and thought 'wow'. Then when I watched it a year later I thought 'Oh my god'. I must have done some growing up between viewings.
Good topic!