Without a doubt the most interesting strain I've had is Durban Poison. Some describe it as licorice/aniseed, I think of it as almost exactly akin to silverbeet (chard). Tastes much the same too.
In terms of best flavour, definitely an Amnesia Haze I had one time. Fresh it smelled like walking through a field of mango trees - inviting. After grinding, it smelled like the ripest mango you could imagine, right under your nose! Simply sublime. Flavour not quite on the levels of the scent, although I did have it in an LB, which can be a bit less flavourful. Still delicious to taste, just more subtle.