The Dunwich Horror, H.P. Lovecraft.
i know Lovecraft is very well known, and therefore almost redundant to put on this list, but his stories were such a formative influence to the kind of media i enjoy that it'd be lacking to not put this on here. this, i will say, isn't his best story - that designation might go to the color out of space, or another story - but i'm fond of this one. while there's much to be said of wilbur whateley and the academics' war against his unnamed brother, my favorite by far is poor lavinia whateley - a character with much potential, left on the wayside.
The Night Wire, H.F Arnold.
a man who copies telegraph dispatches reads the strange, unnerving reports coming through his employee's wire from a town he's never heard of. a short, sweet favorite written in a not-quite-epistolary style. the product of a less than prolific author published three times in weird tales, this one stands out as simple and unsettling - nothing explicit by any means, but it haunts in its simplicity and mystery. a personal favorite for quick rereads and a chilling ending.
each thing i show you is a piece of my death, Gemma Files & Stephen J. Barringer.
incidents and events surrounding people creating an avant-garde independent film festival. wonderfully written in a modern epistolary format, with a unique take on ghosts that's stuck with me long since first reading this story. one of my favorite takes on ghosts and modern media.