Not the wittiest, but the most recent.
A friend (age, late 50s) who likes to drink too much and I were talking. I happened to mention that thing where, when you turn 21, on the day of your birthday if you show your driver’s license to the bartender, you can get a free drink, and lather rinse repeat at various bars until unconsciousness.
She apparently had never heard of this and got very excited.
Until I said, “Ann–it’s too late!”
Cracked her up.
I had a woman co-worker at a former job that was an inch or two taller than I was. She would always refer to me as ‘shorty’. Didn’t bother me a whole lot, but it was day in and day out. Finally, when she called me that in front of 4 or 5 other workers, I said “You’re only calling me that because I have clothes on.” She turned beet red and never called me shorty again.
I’ve told this one before, but I like it, so shut up. 
We were at Fleet Farm (farm & building supply place) and Mr. S was selecting a piece of trim wood for some project from the bins. He’s pretty particular, so it was taking him a while, and I wandered off to go look at something more interesting.
Finally he caught up to me, wood in hand. “Found one!” he told me proudly.
“Yes, I know. I saw the puff of white smoke.”
He cracked right up. Later he said stuff like that is why he’s with me.
Well it certainly ain’t funny without an explanation, so help me out.
mmm
Edit: Nevermind, I get it. 
So that’s why the cashier was asking if you’d noticed the price.