JSFuck (2012)
I probably deserve to get downvoted to oblivion for this but... I've deployed JSFuck in production!We wanted to obfuscate this bit of code, to make life just a little bit harder for reverse engineers. We made this huge function where we pretty much passed in all our application state, and it would run this JSFuck code, and spit out a token. We even made a few tweaks to the code so that you couldn't just reverse it back into JS with something like https://enkhee-osiris.github.io/Decoder-JSFuck/.Performance was surprisingly alright, and it has never hit an environment where it couldn't execute. All in all, a fun few hours setting it up, and I haven't had to touch it since!