This meme requires some thought. I vaguely remember dozens of unforgettable (heh) stories, not necessarily by title. At one time, I read all of Joanna Russ' Alyx stories - love the sly humor. Some stories I've taught just grew stale from repetition - e.g. "The Yellow Wall-paper," "The Lottery," "The Cask of Amontillado," even "First Confession," an Irish Catholic story I taught to a class including a young man fresh from Dublin who didn't seem to get the point - not enough perspective?
I'll try to narrow my list down to 10.