Overton Low F, Overton mezzo A, Sindt D (with feadog body).
These are the whistles that are within easy reach always, but I mostly play flute.
Jeroen
Lately I’ve been intentionally rotating whistles to try to keep the wooden ones all in playing shape. The one whistle that I think is the absolute best is the Thin Weasel E in mopane. Glenn really outdid himself with that one. The two that I’ve really been enjoying are by Ted Wilson (just an overall fine whistle, too bad he couldn’t keep the quality up) and Chris Abell. I had been underwhelmed by the Abell, so hadn’t played it much for some time, but it’s got a nice traditional sound, perfect balance across the octaves, and it’s just SO easy to play.
I’m another flute convert; I’ve been playing mostly my Bleazey boxwood flute lately.
It’s a tie between my Busman and my Elfsongs. I tend to play the Busman when I practice during the day and the Elfsongs in the evening, when everybody’s playing video games (so it’s too loud for the Whitecap but if I play something TOO much louder I hear “Moooom! Can ya keep it down? I’m trying to concentrate here!”).
When I’m out and about, what’s in my pocket varies between my Whitecap, my O’ Briain improved and my ancient Feadog…just kind of depends on who I feel like playing today.
Redwolf
A brass Clare one piece D with a green top I bought for less than 4 Euros in Dublin.
Most often played, right now, aluminum Syn.
Favourite whistle, still the Water Weasel.
g
A Dogwood Busman is what I play the most. It feels the most comfortable and has a special wood character in the sound I like, with really nice deep, rounded, stable, notes. I also like the sound the most.
The second most is a Burke Brass “D” with a Black Tipped Fipple. It has a beautiful clear bell tone across all the notes. Did I say it sounded beautiful. I like the sound almost as much as the Busman, but I like the feel of the Busman better, even though the Burke feels nice.
The third most is Clark Celtic and Clark Sweetone Whistles that I seem to have laying about, but the more I play the other two, the more I play the other two.
Dixon high D
Cook Low D
Around the house: Laughing D (Herbison) (it’s fairly quiet)(This one travels most everywhere with me as it collapses for portability)
In Sessions or public: Burke Al Pro D
Chuck
Burke Alpro D. I change keys sometimes to get a different perspective. Then I play a Burke Alpro E or a BrassPro C.
Current Favorite: Serpent Village Smithy (thanks fenguin!)
All Time Favorite: Elfsong in D 
Burke Narrow Bore D (aluminum or brass, depending on my mood).
At work:
Oak C (gets most of the play)
Sweetone D (unpainted - pretty good, but not as nice as the Oak)
In the car: (stoplights and such)
Self-tweaked Gen Brass D
At home:
Serpent Brassy Polly (gets the most play right now)
Serpent original Polly (gets a lot - very nice whistle)
Oak D (when I want pure and quiet)
Serpent Python Low F (when I have time to warm it up - then I tend to play for hours. My #1 favorite whistle)
I have a bunch of others that get some play - Gen Nickel Bb, D, Eb, Walton’s C, Feadog D, a couple of other Sweetones, Dixon high and low Ds, Walton’s D and Mello D, Clarke original D . . . um, I think I’ve got all the current crop listed, and most get some play. WhOA, me?
The only ones that often get more than an hour a day are the 3 Serpents. I’ve got a Syn D on order - if it performs as expected, it’ll probably bump the Oak D down a notch.
Edit, 1/19/2004 - the Syn arrived, and it did. It’s currently right up there with the Serpent Ds. Very pure whistle (nice contrast to the “rougher” Serpent Polly sound).
My “Oakenstein” (Oak high D with Brass Generation Body), closely folowed by my Burke Narrow Bore D Brass Pro.
Tres
It changes a lot. Currently:
Generation Eb
Sindt D, Busman D
Burke AlPro C
Grinter low F
Copeland low D
whichever Overton is closest.
I hardly ever play anything other than my Oak D.
Occasionally my Copeland high D (nickel) or Generation C.
To those of you who play in the car, be careful! I know someone who got in an accident playing while driving.
J.
Most often:
Hoover whitecap D (whole whistle made by Mack)
Hoover whitecap A (aluminum body - whitecap head)
20 year old Oak (my first whistle)
In the car:
Hoover whitecap on Clare 2-piece body
Mostly I play my flute (Copley keyless), but for whistling it’s almost always my Oak D. On the other hand, I have an Alba Q1 and a Syn on the way, so we’ll have to see whether that changes. Oh, and I currently have a wooden Syn whistle (in Ironwood) as part of its world tour.
Steven
(edited 'cause I can’t spell “Q1”)
Soprano nickel Copeland D, Copeland G, O’Riordan G, Abell delrin D, Abell blackwood Bflat, Burke black tip D. Those are really all I play these days -in the dining room, the den, our bedroom, the living room and my daughter’s room, depending on who’s where when…
PhilO
Oak D
Currently trying to get better on Gen nickel D. Once I sound better on it, I’ll probably go back to mostly playing the Oak.
Old style Generation redtop D (because it’s on my computer desk),Sindt D and Eb,Copeland low D.
My NEW Sindt A/Bb set is getting a bit of stick,because I received them just over a week ago (Lovely instruments!) -but most of my instrument playing time is being spent on my Uilleann Pipes practice set,made by Davy Stephenson,delivered just over a fortnight ago-they are the business(and HARD work!).