T, I agree with you about shingles. Like blues, discussed in another topic, it can be a plural - for example a roofing material. But when people use the word shingles, I think it would most likely be in reference to the disease, where there is no corresponding singular. In fact it is used like a singular noun - "Shingles is very painful." Not "Shingles are very painful."
Minger is a new word to me, but I see it has been defined as UK slang for "an unattractive person; a smelly or ugly person". It's made it into a couple of dictionaries, at least, so it should go into our list. By the way, how is it pronounced girls? One website says the G is hard, but does it rhyme with ringer or linger?