The potential for the application of discrete mathematics beyond computer science: in biology, economics, sociology, etc.
Hal Finney's Reusable Proofs of Work is important for at least two reasons: as a good stab at implementing bit gold, and for its use of the important idea of transparent servers: using remote attestation to verify the code running on servers.
The role of Stockholm syndrome in politics. Left as an exercise for the student. :-)
Three "silent" movies which I've had the good fortune to see on the big screen with live music: The Merry Widow, The Phantom of the Opera, and Safety Last.