Here are a few of the most influential and accessible papers on philosophy of the 20th century, if people are interested in that sort of thing
Conversation
"Sense and Reference" by Gottlob Frege. Probably spawned the entire field of analytic philosophy of language home.sandiego.edu/~baber/metaphy
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"On Denoting" by Bertrand Russell is probably almost as influential as the Frege paper (although a little bit more difficult in my opinion) uvm.edu/~lderosse/cour
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"How To Do Things With Words" by J.L. Austin probably spawned the entire field of sociolinguistics (or at least is foundational) uccstuff.com/FALL2003/j-l-a
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"Is Justified True Belief Knowledge?" by Edmund Gettier is the paper that spawned a million more papers www-bcf.usc.edu/~kleinsch/Gett