What is your magnum opus?

I created a Scheme LISP compiler that assembles to machine code in x86 format. What have you guys done that many people use today?

Jeez where do I even begin.
I authored the FIOC meme, My Other Car, tuna fish, Anal Touring, Touring Complete, Hax My Anus and a whole bunch of other memes. Memes which you use and take forgranted everyday.