There aren't many issues in grammar or usage that scare me much anymore. After years of writing about language, I've learned that the things I don't know — and there are still many — I'm probably not expected to know.
Over the years, that panicky feeling that I'm going to be exposed as a fraud the minute someone asks a question I can't answer has faded away almost completely.
But one issue that can still set my pulse racing is the difference between “anymore” and “any more.” I'm not sure why, but I suspect it has something to do with the fact that I've been getting around to researching it for more than 15 years now. And because I've been “gonna look it up soon” for so long, it makes sense I'd feel a little behind on the subject.