I can one-up all of these. The "snorting snot guy". I work with a guy that refuses to blow his nose. Instead, he snorts his snot up into his sinuses. I can't stand that wet, bubbly sound. I have actually asked him to blow his nose (in a kind way) but he says that nothing ever comes out so why bother... To me, there isn't another sound in the world that will drive me nuts!!