Bands you started listening to after seeing them live

Never been to a big music festival so bands I've seen without knowing are limited but Isis, Baroness, and High on Fire are the main ones I can think of. Isis being the key one of the three obviously.
 
ASPHYX

well I'd listened to them a bit before but not enough to really like them/get into them, then I saw them at MDF in '09 and they ruled.
 
Skeletonwitch for me too, saw them open for Danzig on Halloween in 2008. Been a fan ever since.

U.S. Christmas, saw them with Baroness & I was pretty blown away.

That's really it, most of the concerts I go to I already know all of the bands. Central Illinois Metalfest might change that, as there are several bands there I haven't checked out yet.
 
No, I saw Averse and Nachtmystium at seperate shows. I saw the latter with in Edmonton with two other bands who were so obviously impressive that I forget who they were. The reason I went was because I was offered a ticket at the last moment and decided to go out and enjoy some music. I really liked them after that.

I saw Averse in Houston a few years ago when I was there for work.