[LinuxBender]

Not so much code, but there was a shell script I wrote at a former company about a decade ago as a quick stop-gap to validate static file checksums in Akamai against a code deployment manifest and AFAIK it is still being used today and I don't even work there any more. It's just bash so it should be hopefully maybe super easy to fix when it breaks.

[quisquous]

I wouldn't be surprised if a lot of people have a similar answer! I suspect my longest lasting code is either a quick and dirty shell script or a throw away prototype that ended up in production. I wonder how often the code we obsess over for quality persists versus, say, the code we build in response to a timely, but perhaps less high profile, business need. I'm curious what actually drives longevity.