Well since the only dog I've ever owned is a mix. . .this is pretty easy. It has to be my mystery mutt, Risa.
She was listed as a Border collie cross which is what initially drew me to her (I like herding breeds). I have no idea what mix she actually is but it's doubtful there is BC in there. I think she has some sort of herding breed in the mix and possibly some sighthound. Otherwise, only God knows for certain.
Being my first dog and a 'project' dog, Ris has taught me a lot. Like I didn't know a darn thing about dog training before I got her. Despite thinking I did.
She also has helped teach me to not lose my temper as easily. If I raised my voice to her initially, she would shut down completely. So if I wanted to keep working with her, I had to control myself. It's something I needed to work on anyway.
She's also helped me meet people. I brought her home shortly after I moved out to MT and had no friends. Almost everyone I've met out here I've met through her. No complaints at all.
We've only been together 1.5 years so most of her/our story has yet to be written. Still, despite the setbacks we've gone through, I wouldn't trade her for the world. She's a wonderful dog, even if the world can't always see that.