I love the Puppia harnesses. Jackson has 2 of them so far (well, one is a Puppia look-a-like, but whatever). I love them because they're vest-like so they look stylish but they're also comfortable and easy to put on. Jackson is about 12lbs and wears a Medium, on the smaller end of the Medium.
I also just ordered one of Chattiesmoms silk harnesses as I've heard such wonderful things about them. I got Jackson the color red and I can't wait to get it.
It will be nice to have in the summer-time, as sometimes I think the vest-type could get hot.