I have a Miss Miserable at work.
We got a letter in from a customer thanking us for all our hard work with her and her party (300 guests!) last week. The manager read it out and everyone was really pleased that the customer had taken the time to write to us - except her. She said "I should think so too!". Umm hello?

You're PAID to do this job. All we did was our job. It was nice that our efforts were appreciated by the customer enough that she took the time to write in!
I also had a customer that I needed to sign something, so I grabbed the pen next to me. Standard biro. She snatched it out of my hand and hissed, "NO, that's MY pen.".
I had to go find another pen! There was nothing distinctive about this pen! If I hadn't had a customer there I would have said something immediately. Unfortunately her shift finished and she left before I had finished with the customer, so I was unable to approach her on it. I did tell my manager that I wasn't prepared to be spoken to like that (I am a temp, she is permenant). They apologised on her behalf (which they needn't do) and said that they had a number of issues to take up with this particular employee...