Fiddle
Or violin, if you prefer.
This has been my main instrument for (yes, I'm getting old!) almost 30 years.
Nyckelharpa
The keyed fiddle, typical Swedish instrument. I've been playing a gorgeous one built by Annette Osann for 6 years now. Love it!
Hurdy-Gurdy
Peculiar European folk music instrument with medieval roots and a mighty revival throughout the last 30 years. The One-man-Band of European folk music for many centuries, up into the 1800s: it provides melody, percussion and simple harmonical backing at the same time...!
Diatonic Accordion
My favourite choice when playing for the dance on my own, in particular Breton repertoire: effortlessly powerful, fresh and crisp (the instrument, not me ;-) ). Yes, there are definitely more advanced players than I am. But, yes, I have quite a big repertoire and, so I've been told, my swing's OK as well. So, why not... :-)