Quick rant here.
The one thing I absolutely hate is when you address someone and they just stare at you. I'm always on drive thru and when I recite their order (hello! you had a blah blah blah??) and they just look at me, emotionless, with their card out the window. I didn't realize they were the ruler of the land that doesn't take the time to small talk with the town peasants.
Also when people walk in the cafe and I greet them and they take the time to look at me but say nothing. It takes a lot to smile and ask some of these pinheads how their day was, because I honestly don't care. The least they can do is fake smile since that's what I have to do.