One option is the OPI Simmer & Shimmer (thanks to my dear friend Jocelyn for this lovely gift).
This nail-polish has beautiful metallic flakes in silver, purple, gold and turquoise.
You can wear 2-3 coats for a rich shimmery look, or a single coat over any color (in the pictures above: on top of white). You can also try a shading effect for a more interesting visual effect.
Put a top coat to complete the look. You can also use a matte top coat if you want to 'subdue' the shimmer. The flakes stay in place without top coat, but you wouldn't have a sleek surface.