Built the most generic file importer.
So a customer had his SAP system giving us some 5 million barcodes in a csv which we needed to parse. But as there could be different file types and I thought the handling would always include the same steps I made them configurable through function pointers. - Did not want to make it as spooky as the rest of the code base where the function pointers were buried deep in some shared memory configs, which might even change at run time, but rather I statically used the member functions of my class. Just to poke fun on the ugly C++ syntax of member function pointers. I still shudder at the thought some poor soul now has to maintain that code.
(For the actual parsing I actually used a one liner in awk which was churning through the records in one minute which was faster than the SAP guys seemed to be accustomed to.)