I don't think we can truly share those types of lists. Some people would list as best-ever books that would bore me or never touch me.
But still, besides all those books I really enjoyed but wouldn't force on anyone's lifetime, I'd say some stand out for for me because they left a lingering feeling in me, images and strong impressions, even years after reading them.
The Royal Game by Stephan Zweig. I like a lot of his work, but this novella really blew me way. It's deeply intriguing, touching and disturbing.
Le Horla or The Horla for you english speakers, is the title of two fantastical novellas by Guy de Maupassant, that we studied in school and I read again in adulthood and was left just as mystified. The story is cited as having inspired Lovecraft's "the call of Cthulhu". How can you get any better?
It's about a man losing his mind, or maybe, just maybe, an actual extra-terrestrial being living on water and milk and messing with people's brain. It's tense, it's odd, it leaves strong impressions.
The Girl Who Played Go by Shan Sa, a franco/chinese writer. It's a short love story written in french, pretty dramatic, pretty poetic. Maybe it's because I'm a go player myself, but it left a deeper impression on me as a star crossed lover story than Romeo and Juliette did.
The Metamorphosis By Franz Kafka. It's a favourite of mine I listened to, read by Benedict Cumberbatch dozens of times. So strange, still haven't come to term with all it's implications.
I would recommend any geek/science lover, even the mathematically inept ones like me who do multiplications on a calculator, to read What if? by Randall Munroe, the guy formerly from NASA who does the XKCD comics. It's delightful. He answers the stupid questions of people with scientific accuracy.
Other science or history related books have made my intense delight, but it's not for everyone, so not making the list I guess?
I still consider The Grand Design and The Nature of Space and Time by Hawking absolute must reads.
The adventures of Sherlock Holmes are also on the list I guess?