I have no problem telling guest that I don't have certain songs, but one night I had this guy attempted to hum a song to me and I said man I don't have a clue what you're talking. So he comes back later and says can you play xyz and I say I don't have xyz so he goes my friend is a dj and whatever song I ask him he types it in laptop and it comes up. I just looked at him in disbelief and said I need his magic laptop. So he says are you saying you can't do that.
another great one ive gotten a bunch is "Can i scracth the platter?" or the ever popular variant "What happens if i spin the platter?"
also a favorite "Can i put the headphones on?"
"Can you play something I like?" ...... well wtf do you like?
"You mean you're a DJ and don't have Third Eye Blind?" (wedding...)
"Do you have anything exciting?" .....
"What's this do?" (PRESS)
Those are some lines that immediately come to mind.. another annoying thing people tend to do ALOT is come up and rub the vinyl, THE PLAYING ONE, for a quick wikiwiki, all while holding the imaginary cans over one ear of course.
Oh whats that you say? You wanna out check my soundcloud?
"Could you play that song you know the one with (insert very broad description)" and then get disappointed I can't solve the riddle.