The enote interface only allows 1,500 characters for a post, so I had to pick and choose carefully:
Here are short stories that engage the reluctant readers (and the enthusiastic readers go to town on them).
"All You Zombies," by Robert Heinlein. This is the ultimate time travel paradox story.
"The Green Hills of Earth," by Robert Heinlein. A great story of the power of poetry, the love of home, and the meaning of sacrifice.
"Harrison Bergeron," by Kurt Vonnegut. This provocative story about individuality and equality asks what is beautiful in the human spirit, and why is it feared.
"Do You Want My Opinion," by M.E. Kerr. What would high school be like if sex wasn't taboo, but sharing ideas was intimate and forbidden?
"The Silent Towns," by Ray Bradbury. A funny and sad twist on the last man/woman on Earth story.
"The Veldt," by Ray Bradbury. A children's play room reveals the extent of a family's dysfuntion.
"A Pail of Air," by Fritz Leiber. A truly frightening end of the world story.
The previous list is all classics. For more modern discussion provokers, try this pair:
"Second Person, Present Tense," by Daryl Gregory. What, exactly is consciousness, and why do we need it? The point of view character is a high school girl who has overdosed on a very dangerous drug. Gregory discusses the ideas behind the story at http://darylgregory.com/stories/SecondPersonPresentTense.aspx
"Think Like a Dinosaur," by James Patrick Kelly. A better version of "The Cold Equations," which is a good one too.