The second of the kombucha I sampled from Massachusetts-based Katalyst Kombucha has one of my favourite flavours - Ginger. The ginger that is within is Hawaiian Yellow Ginger.
From the 'Net, I found out that Hawaiian Yellow Ginger is a rare cultivar (less than 1/10 of a percent), that is know for its superior pungency (like Thai ginger is more pungent than Chinese ginger) and depth of flavour. The root is also denser and less fibrous, and very yellow when you slice it open.
This is the kombucha that I tried that had the rather thick scoby on it; I found it a little disconcerting, but there was no real flavour to it, and it went down rather easily, not at all slimy, as I thought it might be. The ginger flavour is strong and shines through the kombucha flavour (which I find weaker in comparison); this is definitely the Hawaiian Yellow Ginger flavour. I would definitely get this kombucha again, of the two that I have tried from Katalyst Kombucha.