Rage Against The Machine
In 1996, Rage Against the Machine were the scheduled musical guests on SNL. They played one song and were banned before they could perform their second song because as they performed, they hung an upside-down American flag behind them. This got them banned from the show.
Martin Lawrence
Martin Lawrence hosted the show on February 19th, 1994 and he ended up having quite the controversial monologue. He made some uncouth references to female hygiene. When the episode was re-aired, that segment was dubbed over with a voiceover by writer Jim Downey. He said that the portion removed: “…was a frank and lively presentation, and nearly cost us all our jobs.” Lawrence never hosted the show again.