I used to work for a large insurance agency, and they used a security guard at the front desk. The morning guard was a chipper gent who would always say "Good morning! How are you?!?!?!" to me and he would get angry at me if I didn't smile at him and say "Fine, how are you!!!" Honestly, in the morning, after a hellish drive in traffic, all I want is to get to my desk and drink some coffee. Some people are just not morning people!
I even started wearing earbuds when I walked in so that he wouldn't expect me to say anything to him. I'd still give him a smile and nod but wouldn't verbally say "good morning" back. One day he finally said, "I'M FINE, THANKS FOR ASKING!" I whipped off my earbuds and said, "I wish you wouldn't do that!" He responded with, "Well, you are really rude for not responding to me every morning!"