In 2012 I was running a Minecraft server for a friend and wrote an initscript to handle it as a daemon, do backups, etc. I threw it up on GitHub and didn't expect anyone to see it. A couple of years later I learnt it was used on commercial Minecraft hosts. Was pretty cool to have built something that other people could tangibly use as income.

I also ratelimited logging in Linux cifs. Now a spammy log message can't hang or panic a client system.

That's probably technically and commercially more impactful but I like my Minecraft script more personally.