I posted about the w7 Metallic Planet collection of nail varnishes AGES ago, you can see the post here; http://helloterrilowe.blogspot.com/2011/11/w7-metallic-range.html, but as you can tell the quality of pictures wasn't very good and doesn't show the colours to their true awesomeness. I've also noticed a lot of people posting about the Max Factor Fantasy Fire nail varnish and being a little dissatisfied with the transparency of it, so that's why I'm recycling the post as they seem a similar concept; having an almost oil slick type effect when the light hits it at certain angles. These varnishes can be found for as low as £1.50 each and the quality is pretty darn good for the price. You only need about 2 coats of the glittery ones to get a nice opaque nail colour.
My favourite is the shit green one, obviously!