Bands I have for my 42mm Gold Sport...
Apple Sport Bands:
Midnight Blue (came with watch)
Black
Stone
Fog
Walnut (should be called "nude")
Blue
Apple Nylon:
Gold/Blue
Pearl
Third-Party:
Shiny Gold Milanese
Flat Gold Milanese
Gold/Silver steel clasp bracelet (heavy and blingy!)
Tough to say what my favorites are. Black Sport is pretty common for me. I also like Stone. I am disappointed in Walnut. Don't like it as much as I hoped.
My newest are the gold/steel bracelet and the flat gold milanese (which I'm currently wearing). The clasp bracelet is definitely the 'classiest' band I own.
To go with that, I also have my Pebble collection: Pebble Steel, Pebble Time black, Pebble Round Silver with silver clasp band. Pebble Time 2 is on Kickstarter order. The Pebbles have the wonderful feature that I can make my own watch face for it that looks exactly how I like. Can't do that with the Apple Watch unfortunately. The Pebble Round is by far the lightest smart watch I own. Elegant looking, too.