Best that I can remember were Delphic supporting Orbital in Sheffield a few years back.
Worst has to be the band supporting New Order at Manchester Apollo last year. Enough kit on stage to launch a mission to Pluto, and all they could manage was a repetitive dirge that didn't go anywhere, even though the drummer worked his backside off. It seemed to be only one track too. Awful. Can't remember the band name, and would only want to know it so I could avoid them in future.