For me, it was as an assistant manager at a video rental store and a retail representative working at retail stores.
As an assistant manager, I've always had weird... yet challenging things happen to me. It was my excellent relationship with the customers that made it easier from time to time.
One guy was checking out a couple movies. He was told by the cashier that he had owed $64 (or something) in late fees. He was like, "What!? No way!" He immediately looked around for me and asked me if the charges were really true. I checked his history and told him they were. He paid without hesitation. He was one of my best customers and he knew me enough to trust me.
As a retail representative, I dealt with managers who were extremely rude and sometimes lazy. When all else failed, I would simply go up the ladder and work with their supervisors... or those supervisors' supervisors... etc.
One time, there was a new product that had to be put out on display. All the stores had received a special display kit. Since it was a new product line, it wouldn't appear on the shelves until a month later. One manager refused to put it up. She kept making excuses like, "I don't have room!" or "I will do it later!" (She said this for two weeks.) So, I talked to her supervisor. He rejected. So, I talked to his supervisor. He rejected. So, I talked to his supervisor. (The next supervisor would have been the store manager. That's how far I went.) He then called in all the other supervisors I talked to and told them to make room for me. They looked at me like I was now their worst enemy and made me space for the display. I was hated by those supervisors for a few months until everything cooled down.
One other thing that made the job challenging was that I had to communicate with hundreds of different people. There would be people with thick beards or heavy accents that made it difficult to understand or lipread them.