This one is in my top twenty. The formula is wonderful, it wears really well and the color is stunning!
Brucci Black Emerald is a deep emerald green in a black base that flashes red/gold. It reminds me of autumn and the way the leaves change colors. You tend to see the duochrome in lower lights which is nice. Also, it's not frosty like some duochromes can be - it's just shimmery.