Piano--expensive, non-portable

Appalachian dulcimer--limited sound output, limited speed potential, limited tuning convenience, jigs are mostly a pain in the a*s. I've gotten comfortable with walking all over the bass and drone strings but my dulcimers in particular HATE to be capoed [sp?] and sound like crap in G or A/Am (I usually tune to DADD and capo, for the sake of convenience).

Hammered dulcimer--unwieldy, tedious to tune, don't stay in tune, loud (not always a plus)

Guitar--I've had very little trouble keeping mine in tune, it doesn't weigh much, and obviously I can slap on a capo and play in any key I need. I personally don't seem have the reflexes to be a great guitarist, although if you just want a solid back-up player, I'm your girl.

Fiddle--expensive if you want a good one, comparatively fragile, requires a lot more practice than, say, a guitar, to be able to play it acceptably in public.