A type of Grammar Nazi who is particular to using the British/Canadian way of spelling words as opposed to the American spellings. Words such as "favorite" or "color" especially annoy the Grammar Nationalist.
Person 1: What colour is your new car?
Person 2: It's a bluish/greyish color.
1: Sorry, what?
2: It's a bluish color like your girlfriend's car.
2: God damn it, you're such a grammar nationalist!