#5: Peace lily.
One of few houseplants that will bloom indoors, the peace lily with its seashell-shaped spathes really will bring a touch of summer into a dreary winter. One of the best plants for removing formaldehyde, it also removes benzene and certain VOCs that are emitted by harsh cleaning products (making it another good office plant, particularly if your maintenance staff doesn't use green cleaners). It also prefers low-light conditions and has a high transpiration rate that will humidify your air. Just be aware that the leaves can be poisonous to pets and children, so peace lily may not be a great choice for new parents or pet owners.