My favorite is the 1980's Australian miniseries, A Town Like Alice.
Then pretty much a tie with
Cool Hand Luke
Full Metal Jacket
And soooo many more! Many of which have been mentioned...
The biggest issue with assembling an AR isn't so much getting the parts together right - it's getting the right parts together. You'll remember the quality of a gun long after you forget how much you paid for it.
US Army 1966-69, VFW Life Member, Retired Geek