Triumphs of the human mind, some not so well-known. People sitting down and finding elegant solutions to problems. Things you'd like to show people 200 years ago.
The Decipherment of Linear B
(Alice Kober, Emmett L. Bennett, Michael Ventris)
"A Very English Genius" - YouTube copy of BBC documentary. As expected, Alice Kober was given little kudos, though I suspect she would have solved it, having been stopped only by her death, which is no one's fault, not even the Romans'. Biggest takeaway from the video, however, is that Michael Ventris' mother was gorgeous.
Simon Singh's "The Code Book" is a nice, digestible read (Chapter 8).
Machine learning (and old-fashioned gray matter) to make shorter shrift of similar problems: Copiale Cipher
Dijkstra's Algorithm (interview): "One morning I was shopping in Amsterdam with my young fiancée, and tired, we sat down on the café terrace to drink a cup of coffee and I was just thinking about whether I could do this, and I then designed the algorithm for the shortest path. As I said, it was a 20-minute invention. In fact, it was published in 1959, three years later. The publication is still quite nice. One of the reasons that it is so nice was that I designed it without pencil and paper. Without pencil and paper you are almost forced to avoid all avoidable complexities."
Constraint Satisfaction is the Holy Grail of Computing. Tell the computer the problem you want solved, and let it solve it.
OptaPlanner, for example.
John Boyd. More of an impact on modern military thinking than Sun Tzu. More than just the OODA loop...
Edward Tufte. There's a method to providing useful information. E.g., the only thing worse than a pie chart is multiple pie charts. Note to IT monitoring product vendors: your stuff wastes too much screen real estate to provide trivial information -- use tables instead.