"Paths of Glory" is one of Kubrick's most underated films (or at least lesser known) and the ending is pure emotional power.
The fact that you just spent almost 90 minutes hating humanity and the shitty situations in which we put ourselves as a species, only to be able to come away from the film thinking "we're not all bad" because of what happens in the final 10 minutes blows my mind.
If you haven't seen it, I can't recommend it enough.
"On Blue's Waters" by Gene Wolfe.
If you haven't heard of the Solar Cycle, or looked into "The Book of the New Sun", I can't recommend it enough.
My brother was finally able to finish the fifth book recently after starting the series roughly 10 years ago, and the fact that he immediately started rereading from the beginning is a testament to how well this series sticks with you.