The Banana Nut Bread is my favorite by far. Best dessert juice I've had. I like it with a couple extra flavor shots, not because it really needs it, just because it's so yummy I can't get enough.
I also really enjoy their 555 blend for an ADV. Some others I've like are:
caramel apple
berry cream
lightning
hawk sauce
At under $5 a sample and cheap, fast shipping, try a few! Many of Mt. Baker's are better after some steeping, so if you don't like it straight away, try it in a week or two.