Green Mate by Nothing But Tea.  Click to visit their website.Green Mate (in this case from Nothing But Tea) is a particularly interesting one.  It’s not a tea, it’s a tisane, but it does contain caffeine.  Although it only has low levels of caffeine, it does have two other xanthines as well: theobromine and theophylline, so despite being low in caffeine it is high in natural stimulants.  It has a weird effect of giving you lots of energy as if you’ve just had a strong coffee but your heart rate doesn’t shoot up like it does with coffee (or at least, this is my experience from drinking this stuff this morning).  It wasn’t the nicest thing I’ve ever tasted but it was certainly drinkable and far more pleasant as a natural stimulant (although without the immediate kick I seem to get from coffee).