Florian Gilcher wants to give this talk
The ultimate yakshave
If there is one software package just named for immature jokes, it's Leslie Lamport's TeX. It has an incredibly long history - and that on top of another software package with a long history: Donald Knuth's TeX.
Both were created out of necessity and dominate a pretty arcane field: typesetting. I love the history of TeX, as it is an interesting story of tradeoffs, non-standard requirements and solutions that took longer then expected.
If you ever think "we should replace TeX, should be a quick thing", I'm here to convince you otherwise.