Ardebg Alligator.
Had it in a bar on a night out, and was was phenomenal. It was expensive per shot, but I feel we cleaned them out.
It was really really good

Wanted to buy it, was £150 a bottle. Way too much for a whisky.
Finally had some disposable income, £150 for a bottle between friends seemed alright... Now it's £250.
Got to the point where a good memory, nice whisky and friends is worth £250... And its £400 per bottle.
Now it's £500 per bottle, still not worth it.
So many good whiskies for less than £100.

It's not an "investment" whiskey at all. That's the span of 15 years or so. Maybe 500% net over 15 years is a good investment, I don't think so.

One of my mates got married recently, would've been a great opportunity to buy a bottle.
Kinda wish I had... but I also painted his house, helped with a TON of DIY stuff, and a bunch of wedding stuff.
The actual on-the-day-stuff was "just turn up" as far as I was concerned.

One day, the price of Ardbeg Alligator will match disposable income and the occasion.
Till then, I'm sure it will keep increasing beyond my means & commitment