We had a very litigious customer who had an application that ran his complete business process. All of it was built by a third party and it was not to his satisfaction.
So he sued them and gave the project to us.
The aim of this project was to restructure the application is such a way that using a few simple parameters it could we configured to work for a completely different market area. I know, it is all a bit vague but legal issues require me to be slightly reticent here.
There were two main challenges in this project.
1. Managing the customer, especially function creep was a big problem.
2. Complexity of the software, with hidden functions and everything.
We managed to do it, and do it within the time frame we had available. Regardless of the outcome, we already knew the customer would sue us as well, just to try and pull the same trick again. He tried and failed, got thrown out of court.