I feel a bit like an old-timer in liking O'Riordan whistles, which I don't think have been mentioned here. I started playing for my own enjoyment and later on a few weddings, etc., in 2006 I believe it was. I bought and sold many whistles over the years, and ended up with a collection of Pat's whistles in several keys, low C, F, G, A, Bflat, and c, d, eflat, and a few odd sets with multiple bodies, and a very early wood set that includes a flute body. I wouldn't claim they are the 'holy grail' by any stretch, but for me, I still find them easy to play and they were made by a great guy, may he rest in peace. There have been a few along the way that I wish I'd kept, too. I owned at various times 3 or 4 'Greenwood' whistles by Michael Boisvert that were very much O'Riordan clones from a construction standpoint, but all in interesting wood species, and one of them in particular that was purple gidgee as I recall, stood out among the crowd. It had a clear very 'pointed' tone that was loud enough to peel paint from the walls. There was a low F and high D by Michael Grinter that was as beautiful as whistle making gets in every way - visually and musically, at least IMHO. I've hung onto a small scale brass D by Mack Hoover that has a tiny, sweet voice that taught me a lot about breath control, for sure, and a Glen Schultz Water Weasel gray PVC in "A". I've spent a lifetime doing pipe organ work and voicing, and while I could get a little hung up on the nuances of tuning, I don't because most of the repertoire doesn't lend itself to long, sustained notes where it would be most likely noticed, at least, IMHO. For a tube - of metal or wood or plastic - I think a little latitude is in order.
"Those who can make you believe absurdities
can make you commit atrocities." - Voltaire