My idiolect
I first seriously entertained the idea of becoming a linguist when I got to college and my new friends noticed certain peculiarities of my speech. Up to that point, I'd never realized how much variation there is between what two people think of as the "standard" form of a language. This realization was helped along by the fact that I was raised in a little island of linguistic oddity known as Pittsburgh. Barbara Johnstone at CMU has studied Pittsburgh English and put together a website, but here're some of the features that people have noticed in my idiolect. If you haven't before, I'd suggest you think about the unique features of your speech; it can be pretty rewarding to find the little quirks that separate your usage from the white-bread standard!

"This needs washed" and "this needs to be washed" are both equally grammatical to me. "This needs washing" sounds affected and questionably grammatical, even though that's standard in most of the U.S.

Positive anymore! "It seems I'm always wearing these shoes anymore" means the same as "It seems I'm always wearing these shoes these days." Other people are confounded by this one, but it's prefectly standard in Western Pennsylvania.

"My one friend" is the same as "one of my friends". It does not imply the speaker has only one friend.

The /i/~/I/ (near-)merger means that I put very similar vowels in "steel" and "mill", so it sounds like I'm saying "still meal" when speaking quickly.

I vocalize /l/s after back vowels, meaning that I pronounce "vowel" more or less the same as "vow". Same with "towel" and "tau" or "cow" and "cowl".

I pronounce the final vowel in "museum" to rhyme with "ham", though no one else I have ever met, my parents included, do so.