Let's go ahead and start with the obvious: Marshall Mathers (a.k.a. Eminem, a.k.a. Slim Shady) has been rapping about hating his mother since the beginning of his career, when he announced to his fans, "Hi, kids, do you like violence?" His lyrics talk about everything from murder to rape to abusing every drug imaginable, and he attributes all this to the hatred he has toward his mother to the lack of love and guidance he got from her growing up. She's not keen on him, either, and has tried to sue him in the past, though he's made plenty of conciliatory advances in recent years.
GG Allin & The Murder Junkies
GG Allin -- birth name Jesus Christ Allin -- died of a heroin overdose in 1993, but despite the fact that he's no longer around, his fan base is growing. He spent his nights on stage flinging his own feces and urine on stage, cutting himself, and threatening to kill himself while performing. He had lyrics about racism and pedophilia, and when he was alive, he wanted "to make rock 'n' roll dangerous again." He also was imprisoned for assault on a girl, whom he reportedly cut and whose blood he drank. As you can imagine, all this would just scare your mom to death. Rightfully so.
The king of freaking moms out. My mom still can't even say his name in a sentence without adding the word "antichrist." Manson's done his best to earn his reputation -- and the image of his face on posters and shirts serves as a pale, made-up visage exemplifying exactly what moms hate most about music.