One of my least appealing characteristics (or most appealing, depending on your point of view), is my pedantry when it comes to the English language.
It's probably not a bad thing, given that I spend an inordinate amount of time using the Mother tongue; eight hours a day for The Man and then some more when I get home. However my obsession with correct usage does have its downsides.
Katie once threatened to leave me stranded in the middle of Tesco when I started going on about the 'Ten items or less' sign. Of course, it should read 'Ten items or fewer' (typically, 'less' should be used for a reduction in quality, 'fewer' for a reduction in a quantity) but this isn't an argument that works when your arms are full of lasagna ingredients and you can't find your Clubcard.
Spending any time on Internet forums (and in this context one doesn't have to use the plural 'fora', we're not ancient Romans, for Juno's sake) is a real trial. The next person to use 'should of' when they mean 'should have' is likely to feel the sharp end of my digital tongue. Which isn't a nice image for anyone.
Rebuff, repudiate, rebut, refute or reject? Ooh, that's potentially a nice night in for me. I was nodding along to the radio tonight when someone explained that technically you cannot work your way up to a crescendo (musically a crescendo isn't a peak, it's the building-up bit before the ultimate end - the correct term would be, erm, climax). I'm surprised I'm married, sometimes.
I spend real time agonising over the correct use of 'affect' and 'effect'. And don't get me started on apostrophes (although starting a sentence with a conjunction is alright these days, so long as you're careful).
I once had a conversation - OK, an argument - with an accountant at work who wanted to write a sentence including the phrase "this will reduce it's margin" in a presentation. This is a particular bugbear of mine. I should have had "the possessive form of its has no apostrophe" tattooed across my belly but "Thug Life" was somewhat less painful. He wasn't having any of it. He was determined. I was frustrated. I actually heard myself saying, "Look, Integer Boy, you look after the numbers, I'll deal with the words."
Not a proud moment.