6. Mystique Raven Darkholme
Even her name suggests mystery and intrigue Raven Darkholme is a mutant shape-shifter who once led an incarnation of the Brotherhood of Evil Mutants, masqueraded as a member of the German aristocracy, and as a deputy director of a top secret defence committee within the American government. Mystique keeps her background as varied and as shadowy as possible. A mastermind (unlike the shapely "hired hand" of Magneto popularized by Rebecca Romijn) and expert markswoman and hand-to-hand combatant gifted with a regenerative healing factor, Mystique's life is a series of switching identities and living on the run for a variety of reasons. Throughout her various appearances in Marvel comic-dom, she mostly shows up as one heck of a nasty bad girl, though recently she managed to land a position in Wolverine's faculty at the Jean Grey School for Higher Learning, teaching ... what you would expect: Introduction to Evil. For a valentine's present, Mystique would probably gift you with an item of extremely high quality and great price ... and then leave you to be implicated in its theft. Now that she has your finger-prints, her identity is safe.