One of the worst (and funniest) I've heard (and I'm sure the perpetrators would agree) was at a song & tune session. Two of my friends decided to have a go at The Eagles' New Kid in Town - despite several beers, total lack of practice, and with just a printout of words & chords to work from.
They went and sat at one end of the room (in the sort of stage-ish area), and commenced. One can only say that it went from bad to worse.......rapidly
Meanwhile, their girlfriends and I looked at eachother first in horror, then in helpless laughter.
Terrible!!!!
Fortunately, they are usually very good - so can be forgiven ... just about

KRis