I'm partial to skill No. 3.
On night two of a two-night St. Patrick's weekend set at New York City's Terminal Five, the band had just launched into an encore of “Kiss Me, I'm Shitfaced,” when it invited around 50 people to join them on stage. One of those audience members was an idiot. After doing a seig heil—the infamous Nazi salute—in full view of the crowd and the band, singer/bassist Ken Casey saw him from across the stage, sprinted over, and proceeded to beat the living shit out of him. From the blog Rocks Off:
It was St Patty's Day week, the shows were packed, and people were getting drunk. And Rowdy. Really Rowdy. As has become tradition the band invited the ladies to come onto the stage for their encore of “Kiss Me Im Shitfaced” 50+ ladies made it past the barricade and onto the stage and danced the song away. The band then kicked into “Skinhead on the MBTA” and a ton of dudes werre getting past security and the stage ended up being packed tighter than the underside of a real man's kilt. As the band kicked into T.N.T. by AC/DC some moron started seig heiling (the nazi salute) in time to the beat.
Ken Casey noticed this and ran right over to the guy, smashed him in the face, took off his bass and hit him with that and then jumped on him and all out chaos ensued. We could only assume from our vantage point that said nazi got his ass kicked. About 30 seconds later Ken emerged from the pileup with his shirt torn and made his way back to the front of the stage. He strapped on his bass and said into the microphone “Nazis are NOT FUCKING WELCOME at a Dropkick Murphys show.”
The action starts at the 8-minute mark. Watch the left of the stage, and watch for Casey's haymaker. It's pretty awesome.