My braided leather leashes that look like the ones On Lead makes. Not sure if they are the same, as I bought mine at a dog show, but they look the same. I have one black/teal, one black/tan and one tan.
I also like my braided 3ft leather leash from J&J Dog Supplies, and my regular leather ones from them are very nice as well. Boring to look at, but super soft and comfortable.
I like my leather leashes from Karma Collars too. The only thing I don't like about them is that I got the 5/8" ones and I can't clip the clip over the handle which I sometimes like to do if I carry the leashes around my neck.
I use my Mendota slip leads more than anything though. The thin ones (can't remember the width. 3/8" maybe?).
My absolute favourite leash is some sort of double ended/multi-use leash from the UK. No idea what it's actually called or where I could get another, but it's so handy and I love the material it's made of too.