QotD: This Gets On My Last Nerve

What is your pet peeve, the one thing which really drives you mad? 
Submitted by Beki.  

Professionally, I hate when people use apostrophes incorrectly, especially when they are making things plural or conjugating verbs. Argh. I have spent at least a week per semester on apostrophe use alone.

Otherwise, I have this ridiculous pet peeve about people who scrape dip up the side and on the rim of the dip bowl. I don't know why it gets me because I'm not really anal and no one would ever mistake me for super-neat (or even neat at all). I had a guest once who was doing that with tortilla chips and salsa con queso and I had to grit my teeth and resist yelling at him or ripping his offending hand off.