Worst one I saw was a duo who came to our club. They set up a PA (something we never usualy see) played a few Shadows numbers and then started to dismantle the PA and leave while other singers were still on! Not seen them since I'm glad to say:-)

Best I saw at dealing with an off-key loud accompanist. At a session we ran in a public bar a very enthusiastic but drunken bloke insisted on joining in with a very soft and tender version of an Irish ballad.

"Can you do lot's of stuff from Ireland?" asked the agreived performer.

"Yesh" slurred the drunken man.

"Well, f**k of and do it then..."

:D (tG)