I'm personally a huge fan of really dark reds, my absolute favorite color. I like when it's shiny and I love when it's really smooth. I'd like to experiment with other colors though and find a shade that I also really love, but whenever I get a chance to pick out nail polish, it's always black and red.
I'd also really like nail art. I don't paint my fingernails though and don't know if I ever will (at least not until the kids are all grown up), so it's just my toenails for now and I don't know how much nail art you can fit on the little things...