Buying a bottle of cider in Lidl (the nice vintage one, I promise) and the checkout guy said to me, with a wink, "Well, young lady, I'm going to need to see some ID" and then laughed as he scanned it. I'm 45.
I'm now in the age category where it's hilarious to even suggest I might be under age.
Any other examples that I need to brace myself for?