I'm a sucker for Purples and Greens. Stila makes an awesome purple shade called Cassis. It is amazing. Ben Nye also makes a great purple called Amethyst. My favorite MAC purples are Entremauve pigment, Royal Hue shadestick, Beautiful Iris, Purple Haze, Fertile, and Parfait Amour. I would say that Nocturnelle, Hepcat, Star Violet, etc. are more plums (red toned) that purples.
ETA: Urban Decay's Flash is a beautiful purple.