Butt Monkey/Music

Benny, from the Axis of Awesome. Their intro overlooks him, and many of their sketches (The Glorious Epic of Three Men being the only one that comes immediately to mind) place him in the role of the helpless victim in some way.
Flake Lorenz. Literally, as Rammstein's gigs often feature frontman Till Lindemann simulate anal sex on the unfortunate keyboard player with a squirting dildo, and cook him in a pot before setting him on fire. Also doubles as the band's Chew Toy. His entry on The Other Wiki has more details.
Jason Newsted, former bassist of Metallica, was the Butt Monkey of the band the entire time he was a part of them. He was always the target of the band's pranks, his bass playing was almost completely mixed out of ...And Justice For All, and he was hated by the majority of the fanbase simply because he wasn't Cliff. Luckily Rob Trujillo, Jason's replacement, hasn't received much of this treatment.
Most celebrities are butt monkeys of the famous rapper Eminem's jokes in his songs (Kim Kardashian, Dr. Dre, etc.)
2-D of the Gorillaz often fills this role, volleying between The Chew Toy and The Woobie parts. He's quite the Extreme Doormat, especially to the sociopathic Murdoc.
Ruben Valtierra, who handles keyboard duties for "Weird Al" Yankovic while on tour. In part because he's been with Al's band the least amount of time (which is still twenty years at this point), and in part because he does the least on the albums themselves (usually backup keyboards, with Al handling main duties), he gets mocked frequently on tour, humiliated as part of between-song skits, and teased reguarly on Al's website. He didn't get to appear on an album's liner notes at all until Running With Scissors... and was then shown face-down with scissors sticking out of his back. His first non-humiliating appearance in the liner notes is 2011's Alpocalypse.
In Paramore, the band seem to really enjoy making jokes at Hayley's expense. In an unknown amount of clips, if one is being embarrassed or teased, its probably her. Possibly due to her status as the Band's face, possibly on account of being the smallest, or possibly being the only girl. Either way, they really enjoy locking her out of the stage door and threatening to kill her on camera.
Nick "Peanut" Baines, the keyboardist of Kaiser Chiefs, is the Butt Monkey of the band. Just look at what the singer said about him on his Wikipedia page; "He likes to go the front and clap, and while he was at the front clapping, we all went off. Left him there on his own."