Transparent Closet: Light Yagami. He was dating Matt for years in order to use his Shinigami eyes but now that he needs Takada he insists he's not really gay but was only using Matt for the investigation.
Unwitting Pawn: subverted, Misa knows that Mello is using her and doesn't care.
The Vamp: Light used Matt's feelings for him to use him for his Shinigami eyes. Mello uses Misa's feelings for him to help him in his plan.