Usually referring to someone whose actions have ulterior motives, generally sexual; someone who's skeemin/schemin' on someone else. Can also be used in a general sense for anyone who seems sketchy or deceptive, and probably clumsy at it. Probably a combination of skeemin and lunchbox.
Yo, my man has been hangin on Cindy all night, what a skeem box.
Skeem box over here is totally trying to mack on my jaunt.