Apocalypse Now. Full Metal Jacket. Platoon. Top Gun. Black Hawk Down. A Few Good Men. Saving Private Ryan. Kelly's Heroes. Crimson Tide.
If you ask your circle of friends and family what some of their favorite military films are, you could get literally a hundred different answers. You'd probably have to ask a few more friends and listen to another hundred more before you get someone to organically name 2006's The Guardian as a movie they've even heard of.
Just to get a few FAQ out of the way early on: yes, Kevin Costner and Ashton Kutcher did a film together. Yes, it is based on the military. Yes, it is about the US Coast Guard. Yes, the USCG is an arm of the US Armed Forces.