I personally think it's almost impossible to name a favorite band, at least for me, because I listen to different stuff at different times.
Right now, I'd say it's Linkin Park. However, that's mainly due to the Minutes to Midnight hype (which btw is an AMAZING album) which has also brought be back to the older stuff which is always fun to listen to.
There are plenty of others that I'd go through phases of as well. Obviously Kelly Clarkson is one of them if I need more of a pop-ish selection or The Killers for a more alternative type. It pretty much depends on my mood.