I know guitar picks are no new idea of something to print, and I should probably cite just about every pick already on Thingiverse.
However, I designed my own picks based on purchased pick I placed in a flatbed scanner and traced in AutoCAD. I like the feel/thickness/shape of these picks above any others I've tried.
I have included 2 files. On my printer with standard .3mm layer height these translate to 2 or 3 layer picks. 2 layer picks are my favorite although a harder pick is sometimes desired.
Print a bunch at a time! They are less than 15 cents apiece to make your own in cool colors.