1 - The thankless - You lend a hand and do something for someone is it really so hard to say thank you?
2 - The thoughtless - This extends to many people and many areas. From those who run conversations on their phones at the checkout, to the boss who alters your schedule without letting you know, to the idiot on the road who pulls into your lane - in front of you without so much as a signal light on, and the people who just show up uninvited to your house because 'you are such a close friend'. To them show a little consideration to your fellow human beings.
3. - The stupid - People who read your name tag and ask if that is really your name. No, I had nothing better today than try to make a fool out of you. People who try to use a coupon that is six weeks expired but can't seem to understand why the store can't take it. The people who show up to make a return of something they bought a year ago, but it isn't open, so you should just wait while they scream how they don't understand why the store won't return this and how they are such great customers. Sorry, but if you were a great customer, you wouldn't wait a year to return something. Hell if I have something I don't need I'm back with it within a day or two, not eleven or twelve months. Wake up and smell the coffee.