CorvusCorax
'Do you come here often?'
I've been known, when a smaller dog is allowed to approach mine, to say loudly to my dog "Oh, look, an apericube! I thought you were looking a bit hungry after skipping breakfast."
Seems to work, though whether its because they're scared my dog will actually eat theirs or of the crazy lady holding the lead is debatable.
I have done 'Lunch!' and 'Aw look, he's the size of your head' with the lads in the past but it was more a joke with a jag.
The most fun I ever had was when a little white thing ran at us barking so I started screaming 'EEEEEK!) and running away in the other direction.