I like Earl Grey but I never understand how people can drink just that. I'd get stomach ache if I tried to have 7 cups of Earl grey a day. I space it out with some Ceylon or some green tea.
I also really love chai, despite it being basically the tea equivalent of those hipster coffees with the spices. Cloves and pepper work surprisingly well in tea.
I also have some Yerba Mate from south America, a vaguely tea-like plant high in caffeine with a very earthy taste. it took me ages to find a place that sells it here. I'd like to drink it at work for the stimulant effect, but It's kind of a messy process compared with teabags.