The entirety of the works of Fabrice Bellard. QEMU and FFmpeg are the most well-known ones, but there's also a full blown x86 emulator fully and exclusively written in native JavaScript, a greenfield image compression format, a JS engine and probably a dozen other things I only randomly stumble upon and think "oh, wtf, another Fabrice Bellard thing?".
On several occasions, I’ve seen some outlandish claim or another on a new piece of software I’ve never heard of, started to roll my eyes, saw that Bellard had written it, and turned back to see what genius thing he’d come up with.
“New Halting Problem solver,” ok, sure buddy, “by Fabrice Bellard”, ok, so tell me how this works…
Matthias Wandel - I'd used jhead for years, and I've watched "that experimental woodworking guy on youtube" for years - it was a bit of a mental "record scratch" when I realized they were actually the same guy.
For John Bradley, it is xv and xcalc.
For Hisham Muhammad it is htop and LuaRocks.
And for Jason Donenfeld it is wireguard and cgit.
Perhaps some of you have other examples.