BTW, my theoretical favorite of those is the engine clone of Carmageddon, made by one guy in C#—however he's finished everything besides power-ups, and then abandoned the project.
I post that each time an open-source clone is on the front page—which is pretty much once a month, sometimes sooner. The site itself was posted on HN three times altogether—one of them in the last hour, again without any traction. This dynamic is kinda funny.
(Correction: there are more posts if I search for ‘http’ instead of ‘https’.)