The Communist Party of Ireland is still functioning, sorta. I have a lot of time for them. They're irrelevant politically, of course, although they still manage to do some genuinely useful things (running the excellent Connolly Bookshop and holding free Irish language classes, for example). They would be fairly sectarian, as are all the left wing parties in Ireland, but I find them less ... bilious than most.
http://www.communistpartyofireland.ie/