(The Customer is) Not Always Right/Heartwarming

A few of these as well.
Also: Sometimes, the customers are the better people.
This, too.
"Are you thankful for me?"
The cashier story qualifies as well.
And this one.
That was sweet of him.
Anytime the customer or whoever realizes and apologizes for being stupid/psychotic/irrational. This shows that not all customers intentionally think they're better than the storekeeper/whatever.
This, in an odd sort of way.
Everyone needs hugs.
"Why don't you take a break? We don't mind waiting."
- don't mind me I just have something in my eye
"Don't worry about it, Jesus and my mama still love me!"
One big hearted postal employee.
It might have been a joke, but this customer definitely qualifies.
"Happy birthday!"
It's customers like this woman who make working in retail a little more tolerable.
Not heartwarming in the usual sense, but it's hard to read this without going "D'awwww."
This inversion of the Peking Duck Christmas. A group of Chinese people become regular customers of a kosher deli to return the favor of Jews often eating Chinese takeout on Christmas.

Here's two to start.
Sometimes, one moment fixes everything.
"It would be so nice to date a girl who's not obsessed with her appearance. May I?"
- Bonus points to the boy for putting the girl's bully in her place.
This guy couldn't afford a ring. His fiance doesn't seem to mind.
- That's adorable. I seriously hope they stay together.
Sometimes, it's good to be wrong.
He thought she'd say no. She said yes to so much more.