I would like to highly recommend Agastache 'Black Adder'. It is not as well known as many in the list and not universally available at most garden centers but it is a wonderful, dependable plant. It does not reseed as many agastaches do so is very well "behaved". It blooms a marvelous blue all summer long and is very robust. I have tried growing the pink and red ones but they never winter over, even the ones that are supposed to be perennial. This one I can depend on to reappear each year.