Sorry for chiming in but I can't help it.
There isn't really one if you mean for investing purposes. Sure, you can get lucky with sets likes the Zombies and 41999. Sets like the new Arkham, Tower Bridge, Sidney Opera House, 10188, Super Star Destroyer give me "moderate" hope but they are already hoarded by people like us or have been available long enough at (or below ) retail price so too many people already have them. As you know, it' small bout supply vs demand,
The "exclusive" and "hard to find" sets have extremely long retail lives nowadays. I seriously doubt we'll see another Eiffel Tower, Taj, Grand Carousel, etc... in terms of ROI.
Back in the 2000s and 2010, anyone could pretty much invest in the cooler sets and make serious coin after a few years. The sets mentioned above along with most UCS, the initial modulars, trains, Batman 1, Harry Potter, and Indy Jones were no-brainers. Jeez, if only I was investing then...
I fear, those days are long gone. We have more investors, longer retail lives (as already stated), less time between retirement and refreshes, and there are far more sealed sets available nowadays than even 3+ years ago in the secondary market.
I do think we can still make money on popular sets that retailed for 6 months to 24 months as long as they aren't refreshed too quickly,