I have two major ones:
1) people who cannot follow simple directions. Today I had to guide a woman step-by-step though the process of using a Debit machine at my store (not an ATM, the debit machines you use to pay at a store)-NOT a big deal. However, when I said "Push the 'OK' button" she pushed cancel, when I repeated she stared blankly at me and said "What do I do?". Also, I specifically told her 5 TIMES that she needed to hold the pen upright to sign because the point was broken, and what does she do? Signs it all 5 times with the pen on a slant, nothing registering.
2) People who feel the need to play the race card, when nothing racial is going on. Also today (i'll make a long story short) a man yelled at me and got nasty, while I was simply talking to him. He wanted to do an exchange, but since we're closing, everything is final sale. I was simply explaining, he was screaming. I told him I could exchange for the exact same thing, same color, diff size. He brought it up in a different color, which I was not allowed to do. When my friend and I told him this, he accused us of yelling at him, and being racist because we supposedly did an exchange for a white woman the night before (we stated she probably had a reciept from before the final sale was put into place, but he INSISTED that he knew she purchased the item the same time he did...SIGH!!!)
Working in retail, I have a LOT of pet peeves, these are just my two main ones...from today!