Although some of these bands have already been mentioned, I'm going to add my little list here because I am new to the forums. (hello!)
This is pretty bad, but I listen to Panic! At the Disco. Only to work out to. But dammit, it's catchy and I like it. ....I'm so ashamed. I also had my Linkin Park phase (Crawling was like, the best song EVAAAR). I had a brief period in about tenth grade where I was completely obsessed with Something Corporate.
But my crowning achievement was the purchase of an incredibly awful album. I bought it on a friend's recommendation, and I hated it, but it was still a part of my music collection:
Good Charlotte.
The fact that I supported this band in any way keeps me up at night. I was in eighth grade, but goddammit, that's no excuse.