dw,
A few years back someone wrote an hilarious bit published in Acoustic Guitar Magazine about the songs people always play-----and the store workers cringe having heard 100+ times a day. Topping the list was "Stairway To Heaven".

For me I usually play "Back Home Again (In Indiana)" though it's funny-----if people ever turn their heads in an obvious attempt to listen to me it's always when I play the opening bars of a James Taylor song (or an identifiable riff from one) Like "Sweet Baby James" , or "Secret O' Life, or "Shower the People".