Whatever you do, stay away from the upright bass. Guys see themselves being made to carry it, and that scares us off. (My wife took up the big bass after many years of marriage, so I had no choice except divorce, and I was afraid no one else would have me....)

If you want to catch a fiddler or mandolinist, the guitar is good, 'cause the guy will consider it convenient to have a rhythm player available whenever he needs it. That works with banjo players, too, but why in heaven's name....?