Here is a fun line I use regularly.

My credit card is wearing-out and often requires swiping a couple times before it is read.

After the clerk swipes it once and it does not work I say "that card should work for sure, I just found it". It is funny to watch how long it takes the clerk to realize what I just said.

I find older clerks just laugh it off as a joke, younger clerks often think about it for a moment, then look up at you to see you smiling back at them. Some never get it and just continue to swipe the card?

My teenage kids find it embarassing when I do stuff like this.

Mike