I love Warning! It's up there with AI, Nimrod and Dookie for me. I don't know why I haven't seen this thread before. It was the second album I bought, only after American Idiot. I love it because the songs are so different, but they're still so good. Maybe because I'm in to music that's a little experimental and strange, it was just really exciting to have one of my favourite bands produce a record like this.
It's also got one of my favourites on it - Castaway. As well as Minority, Deadbeat Holiday, and Misery. They're all so good!