Friend who is not a software person sent me this tweet, which amused me as it did them. They asked if "runk" was real, which I assume not.
But what are some good examples of real ones like this? xz became famous for the hack of course, so i then read a bit about how important this compression algorithm is/was.
I'd say ffmpeg is a good example, it's used by almost every piece of software that has to manipulate audio or video (including messaging applications), yet not many people know about its existance.
And Fabrice Bellard, the original author of ffmpeg, went on to create qemu which pretty much made open-source virtualization possible. Also TCC (even if I don't think that one is widely used), he established a world record for computing decimals of Pi using a single machine that had ~2000× less FLOPS than the previous record, and so much more...