I know they're just doing their job and all, but I get so angry when I am treated like a criminal when I go somewhere to spend my money.
One time, this store had someone dressed in 'normal' clothing follow me around with a clipboard writing down everything I picked up. She was trying to be subtle about it, and I probably made myself seem worse by going into all these random isles to see if she would follow, but omg...I was SO close to telling her off/smacking her. Instead, I looked directly at her, put everything down one by one, and bought what I needed in a store across the street.