Mine was an Oak D for $14.99 on Amazon.com 3 months ago. It works well for me but is it a good whistle? anyway what was your first whistle?
Gen D, but goodness only knows which one. It was a long time ago.
Generation D blue, around 1977. I still have it. It plays well, and I play a bit better than I did in 1977. 
I guess I could also count the Chinese bamboo whistle in C my mom bought me around 1962. I rescued it from a drawer a few years ago, fixed the intonation with sandpaper and putty, and it plays well also.
Sure, your Oak D is probably a fine whistle.
A susato. I wanted a low D whistle, but the nice man behind the counter convinced me to start with a high D. Bad mistake that - the noises I got from the susato diminished my enthusiasm and I almost gave up… (I do not blame the whistle though).
Clarke Sweetone.
Second was a Oak D, and I’ve bought 5 or 6 Oaks since from a local store.
I like them enough to give away to youngsters if they show the remotest interest.
Decent whistles In My Very Limited Experience, and one D and C stay in my collection.
A good Oak is a joy, I’m glad you like yours.
If you are wondering what other good whistles are like get a Freeman Tweaked Mellowdog, or Bluebird.
Also in that general price range are Susatos and the Dixon Trad.
And for a little more the Parks and Hoovers.
I think the Mellow Dog was my third, and still the one I grab when I can play anything.
Collecting whistles is fun, and need not be too expensive.
Just remember that it can take time and recources away from making music.
A blue Generation D long time departed. I don’t even know if anything else was available back then!
A Waltons D that I bought a long time ago. It sat in the box until I quit smoking. Now it’s the standard I’d like to reach with the whistles I make. Haven’t reached that goal yet.
Fedog, A model, like the oldest, payed about a pound for it in the local newsagents, because they sold them for some reason back then. The head disintegrated or disappeared but i still have the barrel though it is horribly warped from being stood on.
Gen red cap, circa '69. Wish I still had that.
Clarke classic with the Bill Ochs’ book and cassette.
I took to the instrument like a duck to water. It began a never ending journey of playing for myself, writing tunes and songs, and performing in public.
Gen D, although I believe I bought a Clarke D and a Generation D at roughly the same time. Bought 'em both from Bob Tedrow.
I bought six all at once in one order: Two Walton’s Mellos [an extra for possible tweaking], Gen D, Sweetone D in ‘natural’ finish [preferred that the English economy get the money because I thought they needed it more, so I didn’t get a Meg], Gen Bb [probably the greatest bargain in the musical instrument world], and a Clarke Original D, painted.
One week later, I ordered a Jerry Freeman tweaked Gen D, a natural finish Clarke Original D, and a Feadog D. After that it was a long time before I bought another whistle. The ones I had taught me much, because of the variety of distinct characters due to every one of those whistles being different except for the Waltons, which played identically, unlike the pair of Clarkes. But I loved that about the Clarkes, and still do.
A Sweettone. I gave it to friends because it wasn’t in tune.
Original Clarke C that came with the Bill Ochs book; at the time, strangely, they had stopped making D whistles.
Philo
It was a Clarke original in C in 1968-9. I do not think there was a book by Bill Ochs at that point but I could be wrong. That was followed not long after by a Gen red top in D. Both seemed to have evaporated from my equipment bag at some point. I have no idea where they went but my band mates favored recorders. Some time in the eighties I bought a Feadog Mk I at an Irish gift shop which I still have. That one got me well and truly hooked.
Feadoggie
a feadog. still have it. still play it…
be well,
jim
Same, 1970.
Soodlum’s - bought at a flea market years ago.
A Shaw D that I bought in a shop while hiking/hitchhiking in Donegal in 1996. I loved it because it was the only one that didn’t contain any plastic…
Bought it together with Geraldine Cotters tinwhistle tutor and thus had a companion during my outdoor evenings there. Only later I discovered that it is somehow out of tune - the lowest note is C# rather than D… 
I still have it in my collection, but I haven’t played it much since…
Georg
Walton D; bought at a Highland Games 'cause there weren’t many choices, had no idea how it would sound. Still love it and the sound, though I think I need to do some tweaking to it (seems to have troubles ever since I detached the headjoint even though all I did was soak it in warm water-- getting breathy-ish squeaks and skips that I never had before I did it. If anyone has any tips for getting rid of that-- silicone grease??-- I’d appreciate it. Hope I didn’t ruin the whistle.)