As a newbie who purchased some "starter" instruments, my favorite to date is my carbon fibre D by Erik the Flutemaker. It sounds true and pure as soon as it is picked up. If I remain true to my nature with other instruments (clawhammer banjos and mtn dulcimers) I will have more in the months ahead.
What are your favorite whistles?
I really love both of my Mack Hoover whistles when I play out at the hospital or nursing homes. But I tend to grab a Clark traditional whistle (the one with the wooden fipple) when I go outside to play. I enjoy its breathy sound for airs and hymns that I like to play. The price is hard to beat.