How about "Sure, you can play it, as long as I can grope your date while you're doing so."?

Trouble is, of course, the guy might agree and his date might not be someone I want any contact with.

More seriously, I have several guitars of varying degrees of quality. The better ones, nobody else plays unless he/she can play as well as, or better than, me (there are a lot of those, I assure you), and is cold sober. But I try to make it a point to take one I care less about if I'm going where there are dubbers who may be drinking.

P.