I first heard about ICP in my high school economics course. Somebody had brought in a magazine article about them and we ended up spending the whole period discussing it. We concluded that, if they could get a devoted following and stay true to them, they'd become quiet millionaires. More than 10 years later, I'm very happy to see that our predictions came true.
I was introduced to their music during a rough time in my life by some people who'd had even rougher lives. Though I'm not a devoted follower, I do like several of their songs and I'm increasingly impressed by the Dark Carnival mythos. They are fantastic story-tellers and they seem to encourage that trait in the artists they develop.
If you can stomach the lyrics, which tend to the cartoonishly violent, the ICP discography would be a great listen for any writer.