A man in the Kansas City area was attacked with a knife and frying pan. He responded by swinging a banjo at his attacker's head:
http://www.kansascity.com/2010/09/14/2222279_overland-park-man-uses-banjo-in.html via MArooned | Photo (unrelated) via Flickr user mahalie used under Creative Commons license
Police say the Monday banjo blow to the head stopped the assailant, who was treated for a cut and taken to jail.[...]
The two 21-year-old friends were drinking and arguing about a band when Hilton grabbed the kitchen weapons and attacked, police said.
The victim happened to have banjo in hand and used it in self defense, they said.
http://www.kansascity.com/2010/09/14/2222279_overland-park-man-uses-banjo-in.html via MArooned | Photo (unrelated) via Flickr user mahalie used under Creative Commons license
Red: [pauses and stares at Bob] A banjo, Bob?
Bob Pinciotti: What? I'm helping!
Red: Where's he gonna get a banjo?
Bob Pinciotti: I don't know! But I saw a guy get hit with a banjo once, and he went down.
Red: [pauses and stares at Bob again] Hitting a guy with a banjo, is dirty.