When I was a very junior EE I ended up working mostly on microcontroller code. There was one bit of extremely ugly code I inherited that parsed a terribly designed serial communication protocol by using a giant maze of nested if statements. I really wanted to rewrite it to something better, but I never quite came up a solution while I worked there. Years later after I was no longer at the company I had a stress dream about it and finally came up with a working solution. I still wish I could go fix it. I really hope it's no longer used, or that someone else has finally fixed it.