Yes you can get cheap mobiles from there and bring them here for unlocking...which is not legal BTW. Your cousin will have to sign a two year bond/agreement with the service provider (in most of the cases it is two years), if he breaks it, the act will be punishable under US laws...if he wants to legally terminate the agreement he will have to shell out money more than it costs to purchase a new handset...
You can however ask him to bring:
MacBook Air laptop
Ralph Lauren Notorious perfume
Ferrero Rochers chocolates
Kisses chocolates
Bose Home Theatre
A good handycam or a digital camera
Cheap Pen Drives
American Eagle, Aberocrombie & Fitch t-shirts
etc. etc.