Shittiest experience is going to a store and thinking the cashier girl is pretty, it gets worse when she helps you out with the buying and is genuinely a funny and nice girl.
Awful experience, you crush on her but can't tell her, cuz she is literally just doing her job, it's the whole idea. She's a delight to be around, so you will end up buying stuff.
I feel shitty everytime, like, she must go through so much annoying shit at customer service, so much bad customers cussing her out, harassing her etc.
And if I tell her I think she is great and that I would like to take her on a date I will become one of the daily hassles she faces.
TLDR: if cashier nice, don't flirt, being nice is her job.