'King of the Underground' had to fight to protect his title. He also had to regularly strip naked, cut himself, got beaten by his fans and throw his own fecal matter at the crowd.
GG Allin's Crazy Fights
Billie Joe Armstrong's Jump Kick
Though the guy in the crowd wasn't a fan, he ended up going with his girlfriend so he could basically just yell out about how much the band sucked. Armstrong was drunk and lost his temper.
Apparently though once he got in the crowd he didn't hit the guy, he missed and got the guy's girlfriend. He spoke to her afterwards, apologized, gave her a kiss and tickets to the next night's show.
Keith Richards' Clobbering Time
The Stones were playing the Hampton Coliseum in 1981 when a fan jumped onstage and started running toward Mick Jagger. While Jagger was busy singing, Richards decided to take the matter into his own hands. He bashed the guy with his guitar and resumed playing like nothing happened.
Maynard James Keenan's Jiujitsu Skills
Maynard James Keenan is not only a kick-ass frontman, but he actually can kick some ass being an expert in jiujitsu and a veteran of the U.S. Army. One unlucky fan would have wanted to know that latter tidbit before jumping onstage and interrupting the band's performance of "Pushit". Keenan quite casually shuns the fan's attempt at a hug by hip tossing the poor bastard, applying a rear-naked choke hold, then dry humping the guy, all while continuing to sing the song.
Axl Rose Flying Off the Stage
In July 2, 1991 Guns played in St. Louis and that's when it happened. Some biker called "Stump" had been bugging Axl all through the show. At one point, he passed a note up to Axl, who said, quietly "Real fuckin cute, man. Real cute." He then gave the note to a roadie. This jerk continued to heckle Axl and the band, and bully people in the audience for another 45 minutes and when the guy pulled out the camera, Axl called for security (who is comprised of mostly friends of the biker gang this jerk belonged to), who never bothered to do anything. Axl decided to kick his ass, jumped out into the crowd and the rest was history.
What's interesting is, the band kept looking out from a curtain backstage, as if they were coming back out. But as soon as the chairs (ripped up from the concrete floor) went crashing into Matt's kit, the band left.
The incident took place on June 3, 2007, in Fishkill, a small town in upstate New York. Some 15-year-old guy threw a hot dog at the Akon's face. And, of course, he sought revenge. Surprisingly, the idiot who threw the sausage willingly took the stage for beating. Then, Akon proceeded to throw the guy off the stage.
Consequently, he was fined $350 and was sentenced to 65 hours of community work.
Randy Blythe's manslaughter case
This is the most tragic case. In 2012, Lamb of God singer Randy Blythe was arrested in the Czech Republic and charged with manslaughter for pushing 19-year-old Daniel Nosek offstage at a show two year prior and causing injuries that led to the fan's death. Blythe was held in Prague's decrepit Pankrác Prison until finally being released on bail 37 days after his arrest; he was ultimately found not guilty in 2013, when he chose – against the advice of legal experts – to return to the country to face trial.
According to eyewitness statements cited by the Czech newspaper following Blythe's arrest, he was chanting "Come on up" between songs, which, the newspaper stated, may have been intended to invite applause from the audience and not a direct invitation to fans. The newspaper went on to report that the fan tried to climb onstage and was thrown by the singer from the stage, falling backwards directly on his head.