As with ArchiveGuy’s Beatles polls (the clear inspirations for this here poll), there can be only one.
Looks like some are missing…Maybe I’m thinking of different King Novels though…
What was the one with the doctor who gets stranded on an island and has to eat himself?
Survivor Type; from a different collection.
Yeah, that was Skeleton Crew.
Man, I want to go back and read these - they gave me a huge appetite for short stories as a reader.
Here’s the wiki for Night Shift. It has links to summaries of all the stories. I think I want to change my answer from “Battleground” to “The Ledge”.
I don’t have a copy any more and haven’t read it for years. But the one that sticks in my mind is that thing with the rats.
Things that are helpful: Links
I Am The Doorway. Best suspension of disbelief, and the best King ending.
That’s why they used it for the cover.
I also read it (repeatedly) years ago, and this is the one I remember best. Second best is Strawberry Spring. I always think of it when Ted Bundy is mentioned, though they’re not all that similar.
I should go back and read it again. It’s one reason that for years I claimed that short stories were my favorite genre.
Hard to really pick one. The Mangler always holds a special (and horrible!) place in my heart. So I’ll go with that one.
I voted for “The Ledge” but Graveyard Shift is a close second. The mewling blind legless mother rats, some as big as a Holstein calf, out-Lovecrafted Lovecraft.
Now *that *was hard! Every story in the whole book is a jewel, excepting (maybe) The Woman in the Room.
In the end, I narrowed it down to The Boogeyman and Quitters, Inc., but I had to go with The Boogeyman just because it still scares the cheesly old shit right out of me.
I Am The Doorway, Battleground, The Ledge, Quitters Inc. and Graveyard Shift are all terrific, but I voted for I Am The Doorway. Incredibly creepy.
I’m not sure why there’s so much love for The Boogeyman. That one fell kind of flat for me.
I read all of these a looooong time ago, so I can’t comment at the moment but thanks to the OP for making me want to dig out my old copy; I know what’s going to be on my nightstand for the next week 
Also, it made me giggle that a poster named Meatros is trying to remember the story where a man eats himself. And apparently Mr King helped Munch with his appetite for short stories.
God, this was a tough one… That was an AWESOME collection.
I ultimately settled on The Ledge, but also considered Jerusalem’s Lot, Night Surf, Battleground, Strawberry Spring, The Lawnmower Man, Quitters Inc, Children of the Corn, and Last Rung on the Ladder…
Damn. Can we do one for Nightmares & Dreamscapes? I read that at age twelve or so and still hate going to the bathroom late at night, at almost thirty.
I Am The Doorway is a great story, but it makes me sick to my stomach.
I voted for Strawberry Spring. It captured my imagination for days after I read it. I even researched the Springheel Jack mythos because of it.
The Woman in the Room seems to be a deeply personal wish-fulfillment story for King. His mother died quite protractedly and painfully from cancer.
Oh hell yeah. “The Moving Finger” fucked me up for life.*
As for the poll, I voted “Gray Matter,” just because I think it’s one of the most fun to re-read. Good sense of dread built up, but doesn’t hit too close to home.
I seriously considered “I Am the Doorway” and “The Boogeyman,” as they are absolutely terrifying. The Boogeyman is right up there with The Moving Finger for freaking me out at 2 a.m. Now that I have kids, I’m not sure I could re-read The Boogeyman. 
*credit to Crazy People
The Ledge is a great story just begging for a great movie.
Finally scene: Close up on protagonist’s face, gun in hand:You’ve never been known to welsh on a bet. <Dramatic pause> But I have. <Sound of gun going off/.
i think Jim Parsons would be good in the role.
It’s been done: Cat's Eye (1985) - Plot - IMDb