Yes, in the realm of science fiction, the greatest love of all is the kind that exists between ship and captain. And on this holiest of love days, who are we to stand in the way of romance? When it comes to these great loves, we would gladly go down with this ship.
Malcolm Reynolds and Serenity (Firefly)
For Mal Reynolds, Serenity was more than just a vessel to live in, or an opportunity for conducting business. Serenity was a second chance, for everyone on board. The crew and its inhabitants were family, but Serenity was just as much a part of the family herself.
The Doctor and the TARDIS (Doctor Who)
The Doctor and his TARDIS. In all his companions, friends and even spouses, he's really only had one true and great love. And she loves him back. "You stole me, and I stole you," she tells him in the form of Idris in the Neil Gaiman-penned "The Doctor's Wife." She's not very reliable, but she always gets him where he needs to go. He doesn't read the instructions and she's never needed them. Together, they're unstoppable.
Johnny and Lucy (Killjoys)
You know, we've talked so much about man's love for the ship—here, the ship loves the man. And Lucy, the AI spaceship on Killjoys, looooooooves Johnny, her programmer. Never was that more clear than in the episode "I Love Lucy" where Lucy temporarily inhabits an android body and uses it to kiss Johnny. You know. For data. *wink*
James T. Kirk and the USS Enterprise (Star Trek)
The thing about true love is that it is both a gift and a curse. Perhaps one of the best examples of this idea plays out in the classic Star Trek episode "The Naked Time" where the crew of the Enterprise becomes infected with a disease that makes them show the parts of themselves they usually keep hidden inside. An otherwise delightfully goofy episode, it takes a turn to the heartbreaking toward the end, first when Spock admits he never told his mother he loved her, and Kirk admits that his great and constant love for the Enterprise isn't exactly easy.
"'I've got it, the disease. Love. You're better off without it, and I'm better off without mine. This vessel, I give, she takes. She won't permit me my life. I've got to live hers…I have a beautiful yeoman. Have you noticed her, Mister Spock? You're allowed to notice her. The Captain's not permitted…Now I know why it's called she.”
Ultimately, Kirk and co. live to love "her" another day. "Never lose you. Never."
Han Solo and the Millennium Falcon (Star Wars)