I...don't really have a favorite instrument.
...But if I had to, I could use...THE KAZOO! with it's mighty powers, I would, um...breathe fire out of it? That's cool, too, right?
Also, it's annoyance would transcend time, space, and all known reality to annoy the frig out of Sable the Lucario, who would come out of nowhere to try snapping it in two, only to find that it is indestructible. So, I guess it works as a summoning object, too.