When I tell him the goofy kid (who looks like he escaped puberty a week ago) that I need something for a Ford F-100 and he tells me "You mean F-150 right? They don't have F-100's.) At that point in time i kind of want to talk to his dad or whoever is in charge of him at that point.
Another one that is fun to use. When they ask (or any other place) "Are you waiting in line?" The answer to use (and I have) is "Nope I am an undercover Jehovah witness just waiting to spread the good word." Works pretty good.

__________________
Vaya con Dios