My most annoying pet peeve?
I love my steak. If I ask for it medium rare, I'd like it medium rare... not rare, and especially not medium.
Recently, was at a restaurant in Lompoc, CA with some customers. One of my co-workers received her steak faaaaar past her requested medium rare. We were with customers so didn't want to make a big deal of it, but at least did notify the waiter. He simply apologized... nothing else. No "Would you like another?" So we discreetly queried him again later and we said he'd talk to the owner. Waiter comes back... "We can comp you your glass of wine."

Real nice. Reminds me... I have a letter to write.