Well, Skillet has been my favorite band for a long time, but they have recently been replaced by The Letter Black. I stood outside for three hours in the blazing hot sun and ruined my skin for weeks to come, just to see them live. I wear their T-shirts, I listen to them all the time... and I haven't even been able to buy their CD yet!
I must say, I normally don't like bands that scream, but even though they have a couple screamo songs, their lyrics are so melodic and powerful. Plus thier lead singer, Sarah is one of the strongest, most beautiful women singers I've seen in any band.
So, please please check this band out. They have everything from hymns, to hard metal, and they do it all really well.