I like Lincoln Park After Dark, Catch Me in Your Net, Red Like Roses, Black Cherry Chutney, My Private Jet, Here Today...Aragon Tomorrow, Yoga-ta Get this Blue, Light My Sapphire, An Affair in Red Square, Malaga Wine, and OPI Ink to name (quite) a few.
Shatter and Gel polishes are very in right now. I like mixing bold base colors with a Shatter topcoat - Catch Me in Your Net looks electric with Shatter in Black. A very light, shimmery green looks good under white, and next I'm trying a nude color close to my skin tone under black.
Coming from a guy, I find awkward saying this but go to OPI's website. They have a amazing virtual way of trying all their colors. If I pick one, I get really attracted to girls wearing Lincoln Park in the Dark. But the first step for any color to look good is for the nails to be in good even shape -- hands as well as feet.