Compare with prunella... Usually a Spring bloomer...
If you have one that re-blooms, might want to propagate... Although... There is a reblooming prunella in the trades...

Definitely a Salvia of some sort. Hard to tell the variety from the photos. This is a good view of the leaves, can you post a pic from a side view to get a good view of the flower spike?

Salvia. Yes, please take more images of the blooms.

My bad...
Agree with salvia... Was at a wifi that didn't permit me to enlarge the pics this morning....

It looks like one of the interspecific hybrids of Salvia longispicata x Salvia farinacea.

Either Sage (Salvia 'Indigo Spires')
or its dwarf mutation Sage (Salvia Mystic Spires Blue) (cultivar 'Balsalmisp', aka "Mystic Spires")

I believe that there is also a new hybrid with similar parentage but I'll have to search for the name of that one. I've only seen a photo of it.

How long have you had the plant and how tall does it get?

The new hybrid is called Salvia 'Magic Wand' and was bred by Danziger.

http://ballpublishing.com/Ball...

http://www.malmborgsinc.com/in...

Now that you mention it I think it is a "mystic Spires". Thanks everyone!