Back in 2010, I created a line that I had been waiting to use.  I finally got that moment at a music store.

I purchase a small PA for my electronic drum set, and while waiting for Aria to pick me up, the salesman and I were talking.  he then asked me for my name and phone number so he could call me to let me know when they will be having special sales.
he asked me what was my name.  He remembered my last name, but not the first.  I said, "How can you not remember my name when you saw it when I gave you my card?"
he explained how he was bad with names.  I then saw the chance to use my line on him.  I said, "That's okay you have problems remembering names.  I have problems remembering faces."
He laughed and said that line was too funny.