Just listing my favourites out of the dozen or so flavours that I've tasted (no, I haven't tried everything yet -- they rotate flavours, selling around 12-14 out of 20-something).
The green apple and the melon flavours taste *exactly* like the respective fruits. It's uncanny. The nature of the fruits are even reflected in the texture of the gelatti -- apple is slightly more icy, more crisp and sorbetto-like, melon is softer, thicker, a slower fragrant sweetness.
Coconut has the gooey goodness of coconut milk, as well as dry shreds of coconuts.
If you've had a good caffe latte, you already know what the coffee flavour tastes like.