Someone mentioned the George R.R. Martin short story “Sandkings” on MetaFilter. I read this as a kid and it scared the hell out of me. To my surprise, I still think it’s kind of great. And my thirty-year-old memory of the last sentence was word-for-word correct.
I read this in the August 1979 issue of OMNI, a subscription my parents bought me because it sounded educational. In fact what I got out of it was nightmares about sandkings and the understanding that you could sharpen a razor blade by leaving it under a pyramid overnight.
The other really frightening story I remember from OMNI was “Fat Farm,” which according to Wikipedia was by Orson Scott Card and appeared in the January 1980 issue. Remember when Orson Scott Card was good? Looking at the first page of this story on Google Books, it seems he wasn’t as good as George R.R. Martin was, back when I was eight years old and easy to frighten.
Quomodocumque 
My favorite story from Omni (never submit to the publisher’s stupid typography, never!) was Spider Robinson’s “Chronic Offender”, a time-travel pastiche of Damon Runyon, “who knows only the present tense, and sometimes the future”. I had to keep around that particular issue of Omni for years until the story finally appeared in a collection — I may still have it, stuffed away somewhere.
There’s a book to be written about OMNI; people who write about cyberpunk always give it a nod (both “The Winter Market” and “Johnny Mnemonic” appeared there). Just reread “Sandkings.” Lots of Bradbury in there, and behind him, Poe. But well-done…
Was just looking through bound issues from the early 80s in the UW library for a story I was trying to remember and — to my gigantic surprise — I kind of wished I had time to sit down and read through them. Weird fact I didn’t remember: they published Anthony Burgess and Julio Cortazar. I probably didn’t remember this because I had no idea who these people were. Also, in retrospect you can totally see from Orson Scott Card’s stories of this period that he would later become, or maybe already was, a weird obsessive on the subject of moral purity.
I enjoyed reading “Sandkings”, thanks. A while later I had this recollection of seeing this plot before. It might be very old (Greek myth?) but what I came up with was “Gremlins”.
Thanks for pointing me to “Sandkings.” I can see why that would scare the hell out of you as a kid … I’d have to look under my bed every night, and I’m not sure the beach would be quite as fun.
I had OMNI for a while when I was about 10 or 12. I wonder if it was a common gift for family members to give to young nerds?