You know, for someone who doesn't like to be over the top about whisky, you've certainly been starting a lot of new discussion threads, Eelbrook!
(Relax, I'm just stirring and having fun!
The sweetest malt I've ever had was a private bottling of Glen Grant, Cask No. 5003, distilled in 1961 and bottled in 1983. (And then opened and tasted in 2004!!)
However, since that was a one-off, I should probably list a bottling that is more commonly available.
I agree with you that the Glenfarclas 15 is a sweet drop, but there's sweeter going around. Aberlour A'bunadh is a good example. Sometimes, even Ardbeg 10 strikes me as being very sweet.