I'm no expert but I'm always willing to learn. And it's related to science and engineering very directly. For example:
-Espionage and the like from Julius Caesar to the Cold War (cryptography)
-The paradox of the two generals or the coordinated attack (logic)
-Alloys and other materials from the Stone Age to the Bronze Age to Magnesium alloys (materials science)
And then, computers, ballistics, chemical warfare, biological warfare, cartography, the MAD strategy during the Cold War. Some of them very unnerving topics, but very interesting nonetheless.
There are very knowledgeable people here, and I think those would be very interesting discussions.