The best is when they have a large portion of the store dedicated to selling things that cannot be bought without an employee helping. At a walmart I worked at when I was younger there were two aisles of paint to be used in mixing but we never had anyone on the floor capable of running the machine since the store opened until I left two years later. There was also the electronics section which had everything under lock and key and had an employee with the key available maybe a third of the time.
I also saw the deli open frequently with no one manning it. It wasn't closed, just had no one to run the machines
For ultra-budget big-box stores, it can be hard to even find staff sometimes.