This wayfarer pair from Prada has my vote. The wayfarer design is classic and timeless and will look right with everything in your wardrobe. The solid frame and thin temples give this a sleek feel.
I am digging the quiet Prada stamp – nothing fancy, just simple and unassuming. The dark grey gradient lenses provide some external visibility of your eyes so you maintain an adequate dose of mystery.
Get this for US$235 at Barneys.