Used to work in a gas station convenience store 5 years ago.
Young Woman comes in and asks for some cigarettes:
Me: "Sure, could I see your ID please?"
Young Woman: "Why do you need ID? I'm EIGHTEEN!"
Me: "Yes, I just need to see your ID to verify that."
Young Woman: "NO! You need ID to buy cigarettes BEFORE you are eighteen! Once you turn eighteen you don't need ID anymore!"
Me: "Ummm....Errr..." [thinks of 100 different counter-arguments in 2 seconds] "Well..."
Young Woman: [interrupting] FUCK YOU! [storms off]
Me: Have a Nice day ma'am