[Blud]

Ok, seriously this time.

A special mail in to receive a key, code, utilily that would allow you to put the disks away legitmately without resorting to the many ways that (ahem) some people use to protect their investment.
T-shirts are fine, but again there would have to be some way of ensuring that you could get the size that fits you right.
Movies, developer books/diaries, concept art, game music are of no real use or worth the extra cost for me.