Gotta agree with Hell's Kitchen, but I don't think it's really a guilty pleasure for me, I just love it and always have since I discovered it a few years ago.
Another is the Real World. I don't know why, I'm not that proud of it, but something about it is just fascinating.
I also love those VH1 "I Love the 90s or 80s etc." The celebrity commentary/comedians is hilarious to me.