My mother has a big turkey feather but never used it much. I've been told you're actually supposed to get a large, stiff, feather and then peel the "feathery" parts off and use the end that was not attached to the bird.

I prefer the large Fender lightweight picks myself, the ones that are triangular but with convex sides--they don't sound harsh and they're too big to fall through my dulcimer's sound holes. If you're doing reenacting stuff, I once had a friend that glued a feather onto a pick so it looked like she was using the feather, but without the bother of keeping it trimmed.