Piss, Shit, Fuck, Cunt, Cocksucker, Motherfucker, and Tits!
Those are the seven dirty words you are never allowed to say on TV or radio according to FCC regulations. There are many other words, and phrases which are frowned upon, but they are judged according to context.
George Carlin highlighted the surreal quality of our Free Speech laws in his relentlessly sarcastic and joyous comedy routines. He was arrested for using these words in a comedy routine back in 1972. However, the case was dismissed by the Judge citing free speech laws.