"I think I'll adopt a gimmick of giving a free beer to any requester with a song I don't know."

Doesn't that defeat the purpose? I thought the object was to know the songs that people are likely to request - instead, you'd be challenging them to come up with obscure songs that you don't know ... ! Which would be different if you claimed to know virtually every Irish song going - but you started this thread, presumably, because you were unsure if your repertoire was sufficient to the job ....