My old employer used to used a highly complex people management system, made up of around fifteen or so different tools and packages. Apparently this had been the case for decades, so in my spare time, I wrote an entirely bespoke, extensible HR web application that could be easily modified without changing the code. It even supported the weird spider web management structure.

I took it to my area manager, who pushed it up the chain. Apparently the country representative liked it a lot, so decided to bring me on board for an implementation and test case. Fast forward a few months, and people are singing praises. I get a huge promotion, with a sizeable pay bump to match.

Sadly, most of my country was sold out to another org, who decided pretty much straight off to make 90% of us redundant. Last I heard, though, my app is now in use in almost every operating country around the world. Not bad for something I wrote in my spare time.

I'm waiting for them to need modifications, because I never had time to complete the documentation...