The Hitchhiker's Guide to the Galaxy.

Enders Game. The first one, the sequels got a little weird at times

Also Childhood's End.

Stranger in a Strange Land.

Dune. For sure.

Dune.

Leviathan Wakes. I couldn’t put it down! Sleep be damned

Callahans Cross Time Saloon by Spider Robinson.

For books, it's Alfred Bester (The Demolished Man is my favorite, but The Stars, My Destination is fantastic too), Jack Vance (if I had to pick one I'd go with The Languages of Pao), and Stanislaw Lem (The Futurological Congress, followed by Solaris).

For short fiction (short stories and novellas) I'm a Nancy Kress fan. I don't like her novels as much, but it seems like every year it two she brings out a ridiculously great short story.

For movies, I have a clear favorite: Forbidden Planet. There are other good ones (Gattaca, Minority Report, The Martian, and Arrival come to mind), but Forbidden Planet has stood at the top of my list for decades.

Book: Excession by Iain M. Banks. Multistranded space opera at its finest.
Film: Has to be Blade Runner.
TV: The Hitchhiker's Guide to the Galaxy.
Music: Shredisode IV, V and VI by Anchorhead: Darth Metal. 15 minute epic death metal renditions of John William's scores for the first three Star Wars films.

Star Wars, Star Trek, Deep Space Nine, Voyager, Blade Runner, A Space Odyssey, Captain America, Ironman, The Time Machine. There was a series by Pierce Anthony, Juxtaposition, which was of two worlds in one, Fantasy (magic) and Science Fiction. If your other self died in one world a door would open to grant you access to the other world.

Old Man's War by John Scalzi

Early Jack Vance. His sense of humour and irony were delightful!

"The Constitution of the United States of America". By The Fumbling Fathers.

I love the genre and anything that makes me think will just be watched repeatedly. Philip K Dick is a fav.

Stargate SG1. This show embodies all the amazing qualities of humanity. Empathy, compassion, curiosity, ingenuity. By far my favorite sci-fi show. As for literature, well, there is too many for me to spend time discussing, so I will stick with television for this answer.

i can't pick ONE! stranger in a strange land by heinlein was a mindblower but i was already a fan and there is a soft spot in my heart for the door into summer. hmm... maybe, possibly mindswap by sheckley, or fahrenheit 451 by bradbury. i adore ellison but my favorite works of his are nonfiction. the female man by joanna russ. so many! those will do for now.

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Asimov's Foundation series of course, also an old book, "The Mote in God's Eye" look it up. I never read a book twice but that one i did

The Illuminae Files are my favorite recent surprise.

Dune
Stranger in a Strange Land

Halo. The video games introduced me to science fiction. After reading the books, I searched for other sci fi stories.

Dune

Blakes Seven!!!! (Am pretty certain they left out the apostrophe.
I added the exclamation marks.)
TV show from the 1970s. I missed its first release, but caught up with it recently, and loved it.

Book: The Lathe of Heaven Ursula K. Le Guin.
Film: Independence day? Honestly, my brain is at a blockage so just picked one of the favorites.
Show: Doctor Who