I enjoyed singing 'With a Little help from my Friends' by the Beatles. People joined in and it was ok. I heard a great version of 'Things we've said to day', another Beatles song sung by a woman who's name I missed. She sang it to a simple guitar finger pick.
I have trawled the Beatles Complete Song Book for more but to be honest most of the lyrics are pretty poor. I am tempted to have an unacompanied go at 'In my Life'. I remember 2 blokes at a festival singing 'Blackbird' to a concertina accomp. very effective.
One year at a workshop at Whitby Festival the late Kenneth Lovelace was groaning on about the purity of the tradition. Willie Scott, the Border Shepherd respoded with a spoof version of 'The Banks of Loch Lomand'. Sharp et al completely ignored large chunks of the reportiore (?) of country singers and did us all a great disservice.
People should sing what they feel comfortable with. Most of us would feel uncomfortable singing rock or pop at a shanty session, but then again?
I have a thread on dragging rock & pop tunes into dance rhythms, how do you feel about that?