Wow! I feel like I am really behind. 
I only have 4 whistles and a mandolin. Hmm…What should I buy next?
8 whistles…another one coming in a cpl of weeks 
Tenor banjo
Mandolin
Accoustic guitar
bodhran
Not much come to think of it…I’ll have to do something about that 
That does it. Banjo here I come…
BTW, if we’re also counting soft-studios, samplers and sequencers… No! Enough already!
About 30 whistles
Martin Guitar
Fender Banjo
If I was forced to reduce the number I would not part with my:
Alba Q1
Humphrey NB D/Eb
Feadog
If I was starting out and wanted a good whistle I would buy a Feadog and have someone who could play well test it for me. The one I have is in tune and intune with itself. It has a wonderful tone, plays easily and is a great little whistle. I would not give in to buying others in search of a whistle that plays better. I would wait until I could play better. Then I would buy whatever I could afford.
Ron
By comparison, my affliction is not quite so serious:
17 whistles + 1 on the way (Busman yellowheart)
1 mandola
2 mandolins
2 guitars
1 banjo