Back in the 90's, I was very into the Christian music scene. Have tons of Christian bands in my audio library.
I'm sure to forget ones I used to love, but off the top of my head: Pillar, P.O.D., dc Talk, Guardian, Tait, Ken Tamplin, MxPx, Michael W. Smith, tobyMac, Hokus Pick, Audio Adrenanline, Tourniquet, Believable Picnic, Imagine This, The Brave, The Insyderz, and (some) Newsboys and (some) Code of Ethics.
If I had to pick an absolute favorite Christian band, though, it would probably have to be the O.C. Supertones.