The "Entertainer" works out pretty good on the guitar if there is not too much noise and the audience is listening. It would not work on St. Patricks day in an Irish Pug.

When I do substitute teaching for the elementary music teacher in grades K - 6, the kids seem to be quite impressed with small instruments regardless of what you play. Uke's, Penny Whistles, are favorites, while songs like Green & Yeller, Abyoyo, Rattling Bog, etc., usually go over big.