I had a woman go off on me because I reached for the half n half at Starbucks before she did. She asked, "What ever happened to ladies first?" While her being a lady immediately came into question, I simply relied, "This is Starbucks, not the Titanic!"

While I'm on the subject, don't be standing by a door for five minutes with a scowl on your face waiting for a guy to open the door for you. It's a courtesy not a requirement!