It's probably not something I would use, but Hattie was the name of a great-aunt I was close to, and I just got to thinking about it today. BtN says it's a pet form of Harriet, but my aunt was just "Hattie."
It's also the name of Hattie Caraway, the first woman elected to the U.S. Senate (She lived in Arkansas.) and Hattie McDaniel, the first African-American to win an Academy Award, for playing Mammy on Gone with the Wind.
What other Hatties do you know, and what do you think of the name?