Now, if I were picking my perfect anthology there probably would be a Joan Aiken in there, but it wouldn't be The Serial Garden. The Serial Garden makes me cry bitterly and at length, and for a very good reason, ie, it is possibly the saddest ostensibly-children's story ever written in the entire, whole world. Trust me on this.
Which begs the question, what would I pick? Something by Saki, for sure; something by Damon Runyan; probably something from Puck of Pook's Hill; something from The Happy Prince; Zenna Henderson's Something Bright; Edith Nesbit's Man Sized in Marble; if I could remember the author or title*, the ghost story about the little girl's hands, although if I had that my Joan Aiken couldn't be Humblepuppy, which is altogether too similar; possibly Pamela Zoline's The Heat Death of the Universe, although it wouldn't fit with the others very comfortably, but then there needs to be a Ray Bradbury too ... what else?
It doesn't help that I've read an awful lot of short stories over the past awful-lot-of-years, and have a pretty fuzzy memory at the best of times. So, what would you pick?
* Ah, there we go.