When I say unpopular, I'm referring to both the good and (sometimes) infamous FF titles. FF games I'm going to exclude due to popularity on this site/in general: FF1, 4, 6, 7, 8, 9, 10, and 13 (its sequels are fair game), Tactics on PS1/GBA, and Dissidia -any other Final Fantasy, main series or spin-off are fair game to pick
Personally, I love Final Fantasy 3 a lot. It's flawed but I still replay it all the time XD plus it has one of the best OSTs in classic FF (imo)
NOTE: When I'm using "popular" Im using a set of rules I created specifically for this thread which were; how often its cited in threads, how often it comes up in FF threads/"best" threads, and the general consensus but this site and many others have cited or ignored certain titles in the series. Obviously using "unpopular" its fairly subjective, but as stated this is how I'm using it in the context of this thread