The amount of hate for Linkin Park in this thread just baffles me. They brought Nu Metal to a whole different level. They weren't the best live performance when they first started but definitely improved over the years. I loved their first studio album.
I wouldn't know what I think the worst band is, but I agree fully with Curl-6's list of awful performances.
To give some perspective, some of my favourite bands or performers are Tool, Staind, Gojira, John Mayer, Hernán Cattáneo, Ludovico Einaudi, Victor Wooten, Rodrigo y Gabriela, Children of Bodom, Bobby McFerrin, Clutch, Metallica, John Butler Trio, The Dead South, Eminem (more so early years), Vektor,... this list is endless really :P
How dare you disrepect Eddy Wally!!
He's the king of the music!